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Liver Injury Due to Drugs and Herbal Agents


Abbreviations

ALT

alanine aminotransferase

AST

aspartate aminotransferase

CDER

Center for Drug Evaluation and Research

CDS

clinical diagnostic scale

DILIN

Drug-Induced Liver Injury Network

DRESS

drug reaction with eosinophilia and systemic symptoms

FDA

United States Food and Drug Administration

HLA

human leukocyte antigen

NAFLD

nonalcoholic fatty liver disease

NAT2

N-acetyltransferase-2

NRH

nodular regenerative hyperplasia

PAS

periodic acid–Schiff

PBC

primary biliary cholangitis

PSC

primary sclerosing cholangitis

RUCAM

Roussel Uclaf Causality Assessment Method

ULN

upper limit of normal

UNOS

United Network of Organ Sharing

VOD/SOS

veno-occlusive disease/sinusoidal obstruction syndrome

Brief Historical Overview

In 1965, Hans Popper and his coworkers published a landmark paper entitled “Drug-Induced Liver Disease: A Penalty for Progress.” He reviewed 155 cases of apparent liver toxicity, related to 30 different agents, and recognized that the information on the clinical and pathologic characteristics of drug- and toxin-induced injury was poorly organized and would benefit from a systematic attempt at classification. He therefore proposed dividing the pathologic changes into six basic categories: zonal injury, uncomplicated cholestasis, nonspecific drug-induced hepatitis with or without cholestasis, reactions simulating viral hepatitis, nonspecific reactive hepatitis, and drug-induced steatosis. To a large extent the classifications used today are the intellectual children of Popper’s classification, reorganized and expanded. The major additions include the spectrum of drug-induced vascular injury, mainly a consequence of chemotherapy and certain natural products, subcategories of cholestatic liver disease related to primary or secondary destruction of the ducts and the category of drug-induced hepatic neoplasms. Identification of the pattern of injury under the microscope is the first job of the pathologist, because the pattern of injury will determine the pathologic differential diagnosis and help determine the mechanism of injury.

A significant barrier to gaining a comprehensive understanding of drug-induced liver injury is the medical literature itself. The primary literature of human drug-induced liver injury is mainly in the form of case reports and small series scattered across the full breadth of the medical literature. There is huge variation in the quality of individual articles both in terms of the data being presented (including descriptions of pathologic changes) and the extent to which other causes of liver injury are excluded. In addition, because of advances in hepatology over the last forty years, physicians are now better able to diagnose a number of conditions that could be mistaken for drug injury. For example, before 1988 chronic hepatitis C may have been present and been mistaken for chronic drug-induced injury (a factor to consider in reading older literature). Beyond the primary literature are a host of review articles, some of which are highlighted at the end of the chapter. These can be helpful, but most are written from a clinical point-of-view and are published in a wide range of clinical subspecialty journals. There are also a number of recent monographs devoted to drug- and toxin-induced liver injury, and while these are also written from a clinical point-of-view, they can offer significant insight into the pathology of drug-induced liver injury.

In recognition of the need to bring structure to what is essentially an anecdotal science, there have been a number of efforts in the last several decades to scientifically evaluate drug-induced liver injury in humans. Beginning in 1985, the European pharmaceutical company Roussel Uclaf organized a series of consensus meetings in France on adverse drug effects where participants considered fundamental questions of injury classification and causality. These efforts culminated in 1993 with the publication of the Roussel Uclaf Causality Assessment Method (RUCAM), which is a numeric scoring system designed to assist clinicians in assigning a degree of certainty as to whether or not a particular agent is responsible for a particular case of hepatotoxicity. This system is further considered later. In the United States, the Food and Drug Administration (FDA) Center for Drug Evaluation and Research (CDER) has organized annual meetings since 2001 between the FDA, academia, and the pharmaceutical industry to discuss various aspects of drug-induced liver injury. Documents relating to these meetings are freely available on the FDA’s website ( www.fda.gov/Drugs/ScienceResearch/ResearchAreas/ucm071471.htm ). Another recent development has been the establishment of regional and multicenter clinical networks devoted to gathering cases of drug-induced liver injury. Networks exist in France and Spain, in the United States, and in other countries. The Acute Liver Failure Study Group prospectively collects cases of acute liver failure in the United States, a significant percentage of which are due to drug-induced liver injury. An important online resource is the LiverTox website ( http://livertox.nlm.nih.gov/ ), maintained by the National Library of Medicine. LiverTox is oriented towards the clinical manifestations of liver injury from drugs and herbal supplements, but also has some information on the pathology of drug-induced liver injury as well as an extensive annotated drug-by-drug bibliography.

Given the relatively low incidence of drug-induced liver injury (discussed later), one may justifiably wonder why it is so important to correctly identify and classify cases. One of the main reasons is that the subtle clinical presentation coupled with a potentially fatal outcome is of great concern to doctors and patients alike. Confirmed hepatotoxicity sometimes leads to regulatory action. Table 23.1 shows the drugs that have been either removed from the US market or flagged by black-box warnings by the FDA for liver injury. A review of FDA regulatory actions over a 25-year period showed that liver injury was the most common reason for a drug to be withdrawn or have its use curtailed. Furthermore, every year reports of first instances of hepatotoxicity of new drugs appear ( Box 23.1 ), reinforcing the fact that we are unable to completely screen for potential hepatotoxicity in preclinical or clinical trial settings. Correct causal association of a drug with an injury coupled with properly reporting the injury is an important part of protecting patients and can lead to limiting the use of or removing potentially harmful medications.

Table 23.1
Hepatotoxicity Resulting in Food and Drug Administration Regulatory Actions
Data from Lasser KE, Allen PD, Woolhandler SJ, et al. Timing of new black box warnings and withdrawals for prescription medications. JAMA . 2002;287:2215–2220; Watkins PB. Idiosyncratic liver injury: challenges and approaches. Toxicol Pathol . 2005;33:1–5; and Norris W, Paredes AH, Lewis JH. Drug-induced liver injury in 2007. Curr Opin Gastroenterol . 2008;24:287–297 and www.fda.gov/Drugs/DrugSafety/default.htm .
Drugs Withdrawn Black Box Warnings Safety Alerts
Benoxaprofen Dacarbazine Acetaminophen
Bromfenac Danazol Dronedarone
Ticrynafen Felbamate Leflunomide
Troglitazone Ketoconazole Nefazodone
Pemoline Nevirapine
Propylthiouracil Ombitasvir/paritaprevir/ritonavir and dasabuvir
Tolcapone Orlistat
Trovafloxacin Pyrazinamide/Rifampin
Valproate Telithromycin
Zalcitabine Terbinafine
Zidovudine Tolvaptan
Zafirlukast
Dietary Supplements
Kava
Lipokinetix

Box 23.1
Drugs with Recently Reported Hepatotoxicity

  • Anastrozole

  • Atomoxetine

  • Ipilimumab

  • Dronedarone

  • Telithromycin

  • Temozolomide

  • Tolvaptan

  • Tumor necrosis factor alpha antagonists

  • Tyrosine-kinase inhibtors

Incidence and Demographics

It is difficult to accurately assess the true incidence of drug-induced liver injury for any particular agent. To know the incidence, one must have some information about the exposed population as well as some method of identifying all of the cases of injury. A recent population-based survey from Iceland made use of that country’s nationalized health care system to estimate the injury incidence for hepatotoxic agents over a 2-year period. They estimated the proportion of prescriptions that led to liver injury for 10 drugs. The incidence varied from 6 per 100,000 patients for doxycycline to 675 per 100,000 patients for infliximab. The combination drug amoxicillin-clavulanate had the most number of cases, but also had a very large number of prescriptions filled, resulting in an incidence of 43 per 100,000 patients. In large, population-based studies the overall incidence of drug-induced liver injury varies from about 2 to 190 per million person-years, depending on the population studied ( Table 23.2 ). Drug classes frequently associated with hepatotoxicity include the antibacterials, particularly amoxicillin-clavulanate and the sulfonamides; the antimycobacterials; nonsteroidal antiinflammatory drugs; and antiseizure medications. Herbals in the form of traditional Chinese medicines make up a significant proportion of cases in Singapore. The prevalence of injury related to particular agents changes with time. Friis and coworkers examined 1100 adverse drug reactions reported to the Danish surveillance system from 1978 to 1987. Herbal usage by persons in the United States has risen progressively over the last 50 years. In the most recent summary from the US Drug-Induced Liver Injury Network (DILIN), liver injury was attributed to herbals and dietary supplements in 16% of 899 cases. Liver injury accounts for a disproportionate amount of drug-associated mortality. In the Danish study, liver injury accounted for 5.9% of the adverse drug reactions but 14.7% of the deaths. Another study from New Zealand recorded similar findings.

Table 23.2
Estimates of the Incidence of Drug-Induced Liver Injury
Country (ref) Years Method of Case Accrual Total Cases Top Drugs Identified Estimated Incidence per Million Person-Years
United States 1977–1981 Health maintenance organization (HMO) database 9 Ampicillin 2–4 for patients younger than 40
20–80 for patients older than 60
Spain 1993–1998 Referral 107 Acetaminophen, aspirin, ranitidine 7.4 (acute serious toxicity)
France 1997–2000 Population-based 34 Augmentin, nevirapine, atorvastatin 140 (crude rate)
80 (standardized rate)
England 1994–1999 Practice database 128 Acetaminophen, diclofenac, flucloxacillin 24 (with sixfold increased risk if 2 or more drugs suspected)
Spain 1994–2005 Referral 461 Amoxicillin-clavulanate, ebrotidine, antimycobacterials 17 (severe toxicity)
34 (overall toxicity)
Sweden 1995–2005 Practice database 77 Diclofenac, flucloxacillin, azathioprine 23
England 1998–2004 Referral for jaundice 28 Amoxicillin-clavulanate, flucloxacillin 13 for jaundice-related drug-induced liver injury
Iceland 2010–2011 Population-based 96 Amoxicillin-clavulanate
Diclofenac
Azathioprine		 191
United States 2004–2010 HMO database 32 Acetaminophen
Herbal supplements		 1.6 for drug-induced acute liver failure

Surveys of acute liver failure ( Table 23.3 ) show that drug-induced liver injury usually accounts for a significant proportion of cases, from 15% of cases in the UNOS database to just over half of cases reported to the ALF Study Group. The proportion of drug-induced liver failure due to acetaminophen also varies considerably, from no cases in a Japanese cohort to three-quarters of cases in several US and Canadian studies. Besides acetaminophen, other drugs that commonly top the lists include isoniazid, valproic acid, and halothane.

Table 23.3
Drug-Induced Liver Injury from Surveys of Acute Liver Failure
Country (ref) Years Method of Accrual Fraction Due to DILI Total Cases
of DILI		 % Due to Acetaminophen Other Top Drugs
Canada 1991–1999 Hospital database 27% 22 55% Isoniazid
United States 1998–2001 Referral 52% 160 75%
Japan 1970–1998 Referral 95 0% Ecarazine, halothane
United States 1990–2002 UNOS database 15% 270 46% Isoniazid, propylthiouracil,
phenytoin, valproate
Sweden 1966–2002 Adverse drug reports 103 14% Halothane, flucloxacillin, trimethoprim-sulfa
United States, United Kingdom, Canada 1999–2004 Pediatric referral 19% 65 74% Valproate, isoniazid
WHO 1968–2003 Adverse drug reports 4690 6.5% Troglitazone, valproate, stavudine
Portugal 1992–2006 Referral 23% 14 0% Antimycobacterials, sulfasalazine, nimesulide
United States 2000–2004 Population-based survey 54% 35 77%
United States 2004–2010 HMO database 52% 32 56%
DILI, Drug-induced liver injury; HMO, health maintenance organization; UNOS, United Network of Organ Sharing; WHO, World Health Organization

Similar to incidence information, it is difficult to assess the demographic factors that are associated with drug-induced liver injury. Overall, the number of reports of drug-induced liver injury appear to increase with age, but whether this is due to true differences in susceptibility or increased drug usage is not clear. In terms of specific drugs, children are more likely to be injured by asprin and valproic acid and less likely to be injured by isoniazid, halothane, and erythromycin. For many drugs there is either insufficient information on age-related incidence or no apparent age effect. With respect to gender, studies show either more reports of liver-related drug injury in women or similar numbers between men and women. Women are much more likely to develop drug-associated autoimmune hepatitis than men, just as in idiopathic autoimmune hepatitis, although the data may be confounded by prescribing bias.

Clinical Manifestations

Hepatotoxic agents are classified clinically in several ways, but a common categorization is to divide them into intrinsic and idiosyncratic hepatotoxins ( Table 23.4 ). Intrinsic hepatotoxins cause injury in a dose-dependent, reproducible manner, which is usually testable in animal models. They are further subclassified as either direct, in which the agent itself is the poison, or indirect, in which the agent is metabolized reproducibly to a toxic substance. Examples of direct hepatotoxins include carbon tetrachloride, which causes zone 3 necrosis and steatosis, and the herbicide paraquat, which damages bile duct epithelium. Acetaminophen is a typical example of an indirect intrinsic hepatotoxin. Under normal conditions it is adequately metabolized and excreted by the liver, but with high doses, increased induction of cytochrome P450 2E1, or reduced stores of cellular glutathione, it is metabolized to the active metabolite N-acetyl- p -benzoquinone, which can damage the cell. Finally, toxicity is classified by the target of the agent, usually either the hepatocyte, resulting in hepatocyte necrosis (usually along zonal lines), or the cholangiocyte, resulting in duct destruction.

Table 23.4
Classification of Drug-Induced Liver Injury by Toxicity Category
Category and Subcategory Mechanism(s) Other Features Examples
Intrinsic Dose-dependent, experimentally reproducible
Direct Toxin or metabolite reacts with multiple targets, resulting in massive disruption Results in cell necrosis with usually little inflammation Carbon tetrachloride (hepatocytes), paraquat (cholangiocytes)
Indirect Drug metabolite disrupts specific metabolic pathway or selectively affects particular macromolecules Effect depends on targets but usually pauci-inflammatory Acetaminophen (necrosis, steatosis), contraceptive steroids (cholestasis)
Idiosyncratic Low incidence, difficult to reproduce, dose independent
Immunologic Drug metabolite reacts with macromolecules to form hapten for B and T-cell mediated immune responses Systemic symptoms and signs (fever, rash, eosinophilia, autoantibodies), prompt recurrence to rechallenge Halothane, chlorpromazine, nitrofurantoin, erythromycins, phenytoin
Metabolic Susceptibility to injury increased by genetic or acquired inability to detoxify or eliminate injurious metabolites Variable time to onset, absence of immunologic signs Isoniazid, valproic acid, amiodarone

The injury caused by idiosyncratic hepatotoxins is classically described as unpredictable, not dose-dependent, and of low incidence compared with the intrinsic hepatotoxins. Some dose dependence has been suggested by data that show a relationship between the potential for toxicity and the overall dose. Drugs that are given at a dose of 50 mg per day or more are much more likely to be the subject of hepatotoxicity reports. Pharmacogenomics has provided insights into genetic alterations that increase the risk of hepatotoxicity for certain drugs. Idiosyncratic hepatotoxins are subdivided by mechanism of action into metabolic and immunologic hepatotoxins.

Immunologic reactions to drugs have been divided into two more categories: autoimmune reactions that resemble idiopathic autoimmune hepatitis and immunoallergic reactions that are accompanied by systemic sign of hypersensitivity. Autoimmune drug reactions present clinically with elevated aminotransferases, elevated immunoglobulin, and autoantibodies, typically antinuclear antibodies. The onset is insidious and may develop months to years after the drug is started. Arthralgias and rash may be present and biopsies usually show a chronic hepatitis-like pattern of injury with plasma cells (see later). Nitrofurantoin, minocycline, and hydralazine are classic examples of drugs associated with autoimmune injury. More recently, the statins have been implicated in drug-induced autoimmune hepatitis. Immunoallergic reactions differ in that they are usually associated with systemic symptoms of hypersensitivity, including fever, rash, and eosinophilia. The rash can be very severe and some patients will have Stevens-Johnson syndrome. The latency time between starting the drug and the development of symptoms is usually less than 2 months. The symptoms will recur quickly if the patient is rechallenged with the medication. A particular type of hypersensitivity drug reaction termed DRESS (drug reaction with eosinophilia and systemic symptoms), may have liver injury as a component, often mild in comparison with the other symptoms. Liver biopsies are more likely to have eosinophils or granulomas and the injury can lead to vanishing bile duct syndrome. Drugs associated with immunoallergic reactions include many types of antibiotics (including sulfonamides, penicillins, and fluoroquinolone among others), certain anticonvulsants, and allopurinol.

Metabolic hepatotoxins differ from the immunologic hepatotoxins in several important respects. There is a widely variable latent period before the development of jaundice and rechallenge does not cause immediate recurrence of the injury. The systemic features of hypersensitivity are absent in metabolic idiosyncrasy. Mechanisms of metabolic hepatotoxicity include genetic variation in pathways that process and detoxify drugs, competition for metabolic pathways by other drugs, or induction of pathways that lead to more toxic metabolites.

The clinical presentations of drug-induced liver injury are almost as varied as the pathology. Patients may present in fulminant hepatic failure, with painless jaundice that mimics obstruction, with signs and symptoms of portal hypertension, with a mass lesion or with asymptomatic enzyme abnormalities. The onset may be sudden or insidious. Because most drug reactions fall into either the necroinflammatory or cholestatic categories, the biochemical changes in aminotransferases, bilirubin, and alkaline phosphatase are used to categorize the injury into a limited number of categories. In general, injuries that present mainly with aminotransferase (either alanine aminotransferase [ALT] or aspartate aminotransferase [AST]) elevations are categorized as hepatocellular injury whereas injuries characterized by elevated alkaline phosphatase are categorized as cholestatic. Injuries in which both transaminases and alkaline phosphatase are elevated are classified as mixed injuries. The ratio of ALT to alkaline phosphatase after normalization to the upper limit of normal (ULN) for each test is used to categorize this biochemical injury pattern ( Table 23.5 ). In reports of drug injury, the ratio is obtained from the time of onset of the injury. The ratio may vary as the injury progresses. If the patient is jaundiced, then that feature is added to the biochemical categorization. Thus, hepatocellular jaundice is an injury in which the transaminases are the predominant enzyme abnormality and jaundice is present. Note that jaundice may be a component of any biochemical presentation and does not imply cholestatic biochemistries. It is also a mistake to extrapolate the biochemical pattern to the histologic findings. There is, at best, only rough correlation between the biochemical categorization and the histologic patterns of injury described later. Patients with a biochemically hepatocellular injury can have essentially any pathologic pattern on biopsy, including acute intrahepatic cholestasis with minimal inflammation. Biochemically cholestatic injury may show an acute lobular hepatitis pattern without evidence of cholestasis on biopsy. Thus, pathologic diagnostic terms like “hepatitis” should only be applied if tissue is obtained for pathology review.

Table 23.5
Biochemical Classification of Drug Injury
Drug-induced liver injury is categorized based on the ratio (R) of alanine aminotransferase (ALT) to alkaline phosphatase (AP) normalized by the upper limit of normal (ULN) for each test:

R = (Alt/Uln)/(Ap/Uln)
Injury Category Minimum Abnormality R Values
Hepatocellular ALT/ULN ≥2 R ≥ 5
Mixed ALT/ULN≥ 2 2 < R < 5
Cholestatic AP/ULN ≥ 2 R ≤ 2

Biopsies may be done for any of several reasons during the evaluation of drug-induced liver injury. Box 23.2 outlines some of the information that should be routinely evaluated in a liver biopsy done for drug injury. It is unusual to see a biopsy under circumstances where the diagnosis of drug injury is absolutely clear on clinical grounds. The clinical situation is therefore likely to be complicated by competing causes of liver injury or a complex drug history. In such a situation the pathologist can help by carefully defining the pattern of injury and the pathologic differential diagnosis. A biopsy may also be done to rule out significant ongoing injury so that a critical drug may be continued. It is important to document the severity of the injury so that clinical decisions can be made. On occasion, a liver biopsy may be done to evaluate enzyme changes or jaundice in a situation where drug injury is not suspected. In this case, the pathologist can play a significant role in bringing possible drug injury into the clinical differential diagnosis and helping to exclude other causes of liver disease.

Box 23.2
Information Available from Liver Biopsies in Assessment of Drug-Induced Injury

  • Determination of the pattern of injury

  • Correlation of injury pattern with published literature of particular agent

  • Assessment of the degree of injury (necrosis, duct paucity, fibrosis)

  • Identification or exclusion of other competing etiologies of liver disease

  • Pattern of injury may suggest mechanism of toxicity

Microscopic Pathology

The diagnosis of drug-induced liver disease can be one of the most challenging and frustrating aspects of hepatic pathology. Essentially every pattern of liver disease may be observed, including patterns that are mixed and difficult to classify. Nevertheless, having a systematic approach to evaluating the liver biopsy and coupling that with identification of the pattern(s) of injury is the most fruitful approach. Although drug and herbal hepatotoxicity can replicate almost any nontoxic injury, individual agents do not usually show every kind of injury. Furthermore, remember that certain kinds of injuries are more often associated with drugs or toxic agents than other etiologies of liver disease ( Table 23.6 ). Drug-induced liver injury should always be in the differential when evaluating a liver biopsy, particularly one that is done to evaluate an as yet undiagnosed liver injury. Being alert to the possibility of a toxic injury even when one is not suspected clinically can help to keep the pathologist’s mind free of bias when reviewing a case.

Table 23.6
Histologic Features That Should Prompt a Search for Drug Injury
Feature Associated Drug Injury Mechanism
Eosinophils (prominent) Hypersensitivity reactions
Granulomas Hypersensitivity reactions
Zonal necrosis Susceptibility to injury based on zonal variation in enzymes such as the cytochrome P450 family
Massive (Fulminant) necrosis Severe end injury of many drugs that cause intrinsic or idiosyncratic hepatocellular injury
Microvesicular steatosis Mitochondrial injury
Vascular injury Toxic injury to endothelial cells (acute and chronic) is associated with the whole variety of vascular injuries
Mixed patterns
Cholestasis + hepatitis
Steatosis + necrosis		 Mixed patterns suggest multiple cellular targets, a common effect of drug injury. Cholestatic hepatitis is a common pattern of idiosyncratic toxins whereas steatosis and necrosis are observed with indirect hepatotoxins like acetaminophen

Hepatotoxic agents may injure any of the cell types in the liver: hepatocytes, cholangiocytes, endothelial cells, and even Kupffer cells. The primary cell type injured will determine how the toxicity is manifested, particularly for endothelial and cholangiocyte injuries. Primary injury to hepatocyte can result in necrosis, steatosis, and cholestasis. Inflammation can result either by involvement of the immune system in idiosyncratic hypersensitivity reactions or secondarily through recruitment of immune cells to sites of injury. A basic pattern-based classification of drug-induced liver injury is presented in Table 23.7 and an index to injury patterns caused by individual agents is given in Table 23.8 . Pathologic terms like hepatitis, cirrhosis, hepatocellular necrosis, cholestatic hepatitis, and so on, should not be used to describe a drug injury in the absence of histologic confirmation.

Table 23.7
Classification of Drug-Induced Liver Injury by Histologic Pattern
Adapted in part from Zimmerman HJ. Hepatotoxicity: The Adverse Effects of Drugs and Other Chemicals on the Liver . Philadelphia: Lippincott, Williams & Wilkins, Philadelphia, 1999.
Pattern Characteristic Features ALT AST ×ULN a Alkaline Phosphatase × ULN a Non-DILI Differential Drug Examples
Necroinflammatory
Acute (lobular) hepatitis (see eSlide 23.1 , eSlide 23.2 ) Lobular-dominant inflammation with/without confluent or bridging necrosis; no cholestasis ++ to ++++ ± Acute viral or autoimmune hepatitis Isoniazid, sulfonamides, halothane, drugs associated with autoimmune hepatitis
Zonal coagulative necrosis (see eSlide 23.5 , eSlide 1.13 ) Zone 3 or 1 coagulative necrosis, usually without significant inflammation ++ to ++++ ± Hypoxic-ischemic injury (zone 3), herpes and adenovirus usually cause nonzonal necrosis Acetaminophen (zone 3), CCl 4 (zone 3), ferrous sulfate (zone 1)
Submassive to massive necrosis (see eSlide 23.3 ) Extensive panacinar necrosis, variable inflammation +++ to ++++ ± Fulminant viral or autoimmune hepatitis Isoniazid, nitrofurantoin, methyldopa, many others
Chronic (portal) hepatitis (see eSlide 23.4 ) Portal-dominant inflammation, interface hepatitis (also includes mononucleosis pattern), with or without portal-based fibrosis; no cholestasis + to +++ ± Chronic viral or autoimmune diseases, early PBC/PSC, mononucleosis-associated hepatitis Nitrofurantoin, methyldopa, sulfonamides, phenytoin (mono-pattern), drugs associated with autoimmune hepatitis
Mononucleosis-like hepatitis Sinusoidal beading + to ++++ Variable EBV-associated hepatitis Phenytoin
Granulomatous hepatitis (see eSlide 19.7 ) Inflammation dominated by granulomas (usually nonnecrotizing), portal or lobular + + to ++ Sarcoidosis, PBC, fungal and mycobacterial, atypical bacterial infections Phenytoin
Cholestatic
Acute cholestasis (intrahepatic, canalicular) Hepatocellular and/or canalicular cholestasis in zone 3, may show duct injury, but little inflammation + + Sepsis, acute large duct obstruction Erythromycin, estrogens, androgens, diazepam, diphenylhydantoin
Chronic cholestasis (vanishing bile duct syndrome) (see eSlide 23.8 , eSlide 28.2 , eSlide 28.3 ) Duct sclerosis and loss, periportal cholatestasis, portal-based fibrosis, copper accumulation + + to ++ Primary sclerosing cholangitis Floxuridine (by hepatic artery infusion)
Chronic cholestasis (PBC-like cholangiodestructive) Florid duct injury with duct loss, periportal cholatestasis, copper + + to ++ Primary biliary cholangitis, autoimmune cholangitis, chronic large duct obstruction Chlorpromazine, amoxicillin-clavulanate, tolbutamide
Mixed hepatocellular-cholestatic (cholestatic hepatitis, hepatocanalicular) (see eSlide 23.6 , eSlide 23.7 ) Acute hepatitis pattern plus zone 3 cholestasis, inflammation may be very severe with confluent necrosis + to +++ + to ++ Acute viral hepatitis Very common DILI pattern: antibiotics, isoniazid, nitrofurantoin, diclofenac
Steatotic
Steatosis, microvesicular (see eSlide 23.9 ) Predominantly microvesicular steatosis, inflammation variable + to ++ ± Alcohol, fatty liver of pregnancy Valproic acid, tetracycline, azathioprine, didanosine, fialuridine
Steatosis, macrovesicular Predominantly macrovesicular steatosis without significant portal or lobular inflammation, no cholestasis ± to + ± to + Very common finding in general population, alcohol, obesity, diabetes Methotrexate, tamoxifen, valproic acid, many organics
Steatohepatitis (see eSlide 12.3 ) Zone 3 ballooning injury, sinusoidal fibrosis, Mallory bodies, variable inflammation and steatosis ± to + ± to + Common finding in general population, alcohol, obesity, diabetes Amiodarone, perhexiline maleate, tamoxifen, methotrexate
Vascular
Sinusoidal dilation/peliosis Sinusoidal alterations with/without mild lobular inflammation, sinusoidal fibrosis ± to + + to ++ Artifactual, acute congestion, bacillary angiomatosis, nearby mass lesions Androgens, estrogens, glucocorticoids, thioguanine, azathioprine
Sinusoidal obstruction syndrome/veno-occlusive disease/Budd-Chiari (see eSlide 23.10 , eSlide 30.5 ) Occlusion or loss of central veins, thrombosis, with or without central hemorrhage and necrosis + to ++ Variable Chemotherapeutic agents, bone marrow transplant prep regimen, certain teas
Hepatoportal sclerosis Disappearance of portal veins Arteriohepatic dysplasia Arsenicals
Nodular regenerative hyperplasia Diffuse nodular transformation, with or without mild inflammation and sinusoidal fibrosis Variable + Collagen-vascular diseases, lymphoproliferative diseases (but perhaps because of DILI) Azathioprine, thioguanine, mercaptopurine, steroids
Neoplasms
Hepatocellular adenoma Variable Variable Sporadic adenomas Androgens, estrogens, danazol
Hepatocellular carcinoma Variable Variable Sporadic hepatocellular carcinoma Androgens, estrogens, danazol, Thorotrast
Cholangiocarcinoma Variable Variable Sporadic cholangiocarcinoma Androgens, Thorotrast, vinyl chloride
Angiosarcoma Variable Variable Sporadic angiosarcoma Androgens, Thorotrast, vinyl chloride
Cytoplasmic alterations and pigments
Glycogenosis Diffuse hepatocyte swelling with very pale bluish gray cytoplasm + to ++ Type I diabetes Corticosteroids
Ground-glass change Diffuse homogenization of cell cytoplasm due to induction of smooth endoplasmic reticulum Phenobarbital
Cytoplasmic inclusions Discrete PAS positive cytoplasmic inclusions Alpha-1 antitrypsin deficiency Cyanamid
Gold pigment Granular black pigment in Kupffer cells Gold
Thorotrast pigment Grayish gold, refractile pigment in Kupffer cells Thorotrast
ALT , Alanine aminotransferase; AST , aspartate aminotransferase; CCl 4 , carbon tetrachloride; DILI , drug-induced liver injury, EBV , Epstein-Barr virus; PAS , periodic acid–Schiff; PBC, primary biliary cholangitis; PSC , primary sclerosing cholangitis; ULN, upper limit of normal.

a ±: Normal to mild elevation (<3× ULN), + : mild elevation (3–10× ULN); ++: moderate elevation (10–20× ULN); +++: marked elevation (20–100× ULN); ++++: very marked elevation (>100× ULN).

Table 23.8
Index of Drugs and Herbals Associated with Hepatotoxicity
Drug Name Histologic Pattern of Injury Biochemical pattern of injury a Documentation
Necroinflammatory Cholestatic End-Stage Steatosis Vascular Injury Tumors
Zonal Necrosis Lob. Hepatitis Portal Hepatitis Granulomas Acute Cholestasis Mixed Cholestasis-Hepatitis Chronic Cholestasis (VBDS) Primary Biliary Cholangitis-like Primary Sclerosing Cholangitis-like Cirrhosis Fulminant Hepatitis Microvesicular Steatosis Macrovesicular Steatosis Steatohepatitis VOD/SOS Budd-Chiari Peliosis Sinusoidal Dilation Nodular Regenerative Hyperplasia Hepatocellular Adenoma Hepatocellular Carcinoma Cholangiocarcinoma Angiosarcoma Hepatocellular Mixed-Cholestatic
Acarbose X X X B
Acetaminophen X X X X X X T
Acetohexamide X X X X D
Acetylsalicylic acid (aspirin) X X X X X X T
Acitretin X X X C
Actinomycin D X X
Adalimumab X X X C
Adriamycin X b
Ajmaline X X
Allopurinol X X X X X A
Amineptine X X X X
Aminoglutethimide X X
Amiodarone X X X X X A
Amitriptyline X X X X X B
Amlodipine X X X C
Amodiaquine X X X X B
Amoxicillin-clavulanate X X X X A
Amoxapine X Z
Ampicillin X X X C
Ampicillin-sulbactam X X
Amsacrine X X X X X
Anakinra X C
Anastrozole X X X D
Androgens X X X X X X X X X A
Aprindine X X X X X X
Asparaginase X X X B
Atenolol X D
Atomoxetine X X X X C
Atorvastatin X X X A
Azapropazone X X X X
Azathioprine X X X X X X X X X
Azithromycin X X B
Bacille Calmette-Guérin (BCG) X X X
Benorylate X X
Benoxaprofen X X
Benzarone X X X
Bortezomib X X
Bromfenac X X X X
Bupropion X X X C
Busulfan X X b X X A
Calcium hopantenate X
Camphor X
Candesartan X X C
Captopril X X X X X B
Carbamazepine X X X X X X X X A
Carbarsone X X
Carbenicillin X X D
Carbimazole X X
Carboplatin X X X D
Carbetamide X X X X
Carmustine (BCNU) X X X Z
Cefadroxil X X D
Cefalexin X X C
Cefazolin X X B
Celecoxib X X X X B
Cetirizine X X C
Chlorambucil X X D
Chloramphenicol X X X X
Chlordiazepoxide X X X D
Chloroform X X X
Chloropurine X X
Chlorozotocin X X X
Chlorpromazine X X X X X X X X X A
Chlorpropamide X X X X X B
Chlortetracycline X X X X X T
Chlorothiazide X D
Chlorzoxazone X X X X X B
Cimetidine X X X X X X B
Cinchophen X X X X
Cinnarizine X X
Ciprofloxacin X X X X X B
Cisplatin X X X X b X D
Citalopram X X C
Clarithromycin X X X B
Clometacin X X X X X X
Clopidogrel X X B
Clorazepate X Z
Chlorthalidone X
Cloxacillin X X B
Clozapine X X X X B
Corticosteroids X X X X
Cromolyn X X X D
Cyamemazine X X
Cyanamide X X
Cyclofenil X X X X
Cyclophosphamide X X X X B
Cyclosporine X X X D
Cyproheptadine X X X C
Cyproterone X X X B
Cysteamine X X
Cytarabine X X X C
Dacarbazine X X X X X B
Danazol X X X X X X X
Dantrolene X X X X X X A
Dapsone X X X X
Daunorubicin X b X X X
Desflurane X X C
Desipramine X X X X Z
Detajmium tartrate X X X
Dextropropoxyphene X
Diazepam X X X Z
Dichloromethotrexate X X X
Diclofenac X X X X A
Dicloxacillin X X B
Dicoumarol X X
Didanosine X X X A
Diethylstilbestrol X X X
Diflunisal X X C
Dihydralazine X X X
Diltiazem X X X C
Dimethylbusulfan X X
Disopyramide X X X X C
Disulfiram X X X A
Doxidan X X X
Duloxetine X X X X B
Ebrotidine X X X X
Enalapril X X X X B
Enflurane X X X B
Erlotinib X X X X C
Erythromycin X X X X X A
Estrogens, synthetic X X X X X X X X A
Etanercept X X B
Ethambutol X X D
Ethionamide X X X B
Etodolac X X C
Etoposide (VP-16) X X C
Etretinate X X X X X
Ezetimibe X X X X C
Felbamate X X X B
Fenofibrate X X X X B
Feprazone X X
Ferrous sulphate X c
Fialuridine X X X
Floxuridine X X X X X X A
Flucloxacillin X X X X X A
Fluconazole X X B
Fluoxetine X X C
Fluoxymesterone X X X X
Fluphenazine X Z
Flurazepam X X X X D
Fluroxene X X X
Flutamide X X X A
Gatifloxacin X X X X X X
Gemcitabine X X
Gemtuzumab X X C
Gliclazide X X X D
Glyburide (Glibenclamide) X X X X X B
Gold X X X X X X A
Haloperidol X X X X X X X B
Halothane X X X X X X X A
Hycanthone X X X
Hydralazine X X X X X A
Hydrochlorothiazide X X X D
Hydroxyprogesterone X X
Hydroxyurea X X C
Ibufenac X X
Ibuprofen X X X X X A
Idoxuridine X X
Imatinib X X X X B
Imipramine X X X X X X B
Indicine X X
Indinavir X X Z
Indomethacin X X X X X C
Infliximab X X X X X X A
Interferon alpha X A
Interferon beta X X A
Interleukin-2 X X X X X
Interleukin-6 X X
Iodipamide meglumine X X
Iodoform X X
Ipilimumab X X X
Iprindole X X X
Iproclozide X X X
Iproniazid X X X
Irbesartan X X C
Irinotecan X X B
Isoflurane X X B
Isoniazid X X X X X X X X X X A
Itraconazole X X B
Ketoconazole X X X X X A
Ketoprofen X X C
Labetalol X X X X X C
Lamotrigine X X X X B
Lapatinib X
Lergotrile X X
Levofloxacin X X X X B
Linezolid X C
Lisinopril X X X X B
Losartan X X X C
Lovastatin X X X B
Mebendazole X D
Medroxyprogesterone X X X
Mefloquine X D
Meglumine antimoniate X
Meloxicam X C
Mercaptopurine X X X X X X X X A
Mesalamine (mesalazine) X c X X X C
Mestranol X X X
Metformin X X X X X B
Methandrostenolone X X X
Methimazole X X X X X B
Methotrexate X X X X X X X A
Methoxyflurane X X X X
Methyl salicylate X T
Methyldopa X X X X X X X X X X X A
Methyltestosterone X X X X X X X
Methylthiouracil X X
Minocycline X X X A
Mirtazapine X X C
Mithramycin X X
Mitomycin C X X X X X C
Moxifloxacin X B
Naproxen X X X X X X B
Nefazodone X C
Nevirapine X X X X X X A
Niacin X X X X T
Nifedipine X X X B
Nimesulide X X X X X X X A
Nitrofurantoin X X X X X X X X X A
Nomifensine X X X
Norethindrone X X X
Norfloxacin X X X X C
Novobiocin X X
Ofloxacin X X X
Olanzapine X X B
Oxacillin X X X X X X B
Oxaprozin X X C
Oxcarbazepine X D
Oxymetholone X X X
Oxyphenbutazone X X
Oxyphenisatin X X X X X X
Papaverine X X X X X
Para-aminosalicylic acid X X X X
Paroxetine X X B
Pazopanib X
Pemoline X X X
Penicillamine X X X B
Penicillin X X X X C
Pentamidine X X D
Perhexiline maleate X X X X X X
Phenazone X
Phenazopyridine X
Phenelzine X X X C
Phenindione X X X
Phenobarbital X X X X X X B
Phenprocoumon X X X X X X
Phenylbutazone X X X X X X X X
Phenytoin X X X X X X X A
Pioglitazone X X X X C
Piroxicam X X X X X B
Pirprofen X X X
Pizotifen X X
Practolol X
Prajmalium X X X
Pravastatin X X C
Procainamide X X X X C
Prochlorperazine X X X X X C
Propafenone X X B
Propylthiouracil X X X X X A
Pyrazinamide X X X X X A
Quetiapine X X X C
Quinethazone X X
Quinidine X X X X A
Quinine X B
Raloxifene X X X
Ramipril X X X C
Ranitidine X X X X B
Repaglinide X X D
Rifampin X X X X X A
Riluzole X X X D
Risperidone X X X X X C
Ritonavir X X X C
Rofecoxib X X X
Rosiglitazone X X X C
Rosuvastatin X X X B
Roxithromycin X X X
Sertraline X X X B
Sevoflurane X X B
Sibutramine X X D
Simvastatin X X X A
Sirolimus X D
Sorafenib X C
Spironolactone X X D
Stavudine X X X X X B
Streptozotocin X X X
Sulfadiazine X X X X X
Sulfadimethoxine X X
Sulfadoxine-pyrimethamine X X X X
Sulfamethizole X X X
Sulfamethoxazole X X X X
Sulfasalazine X X X X X X X A
Sulfonamides (class) X X X X A
Sulindac X X X X X X A
Suloctidil X X
Sulpiride X X
Tacrine X X X
Tacrolimus X X X X D
Tamoxifen X X X X X X X X X B
Telithromycin X X X X X A
Temozolomide X X C
Terbinafine X X X X X B
Terfenadine X X
Testosterone X X X
Tetracycline X X X T
Thalidomide X X X X C
Thiabendazole X X X X X B
Thioguanine X X X X X X X A
Thioridazine X X B
Thiotepa X X c X D
Thorotrast X X X X X X X
Ticarcillin-clavulanate X X X
Ticlopidine X X A
Ticrynafen X X X X X
Tiopronin X X
Tocainide X X X
Tocilizumab X X D
Tolazamide X X X X X X D
Tolbutamide X X X X X X Z
Tolcapone X X C
Tolmetin X D
Toloxatone X X X
Total parenteral nutrition X X X X
Tranylcypromine X X D
Trazodone X X X X X C
Trastuzumab X X
Triazolam X X Z
Trichlormethiazide X
Trifluoperazine X X X Z
Trimethoprim X X C
Trimethoprim-sulfamethoxazole X X X X A
Tripelennamine X X
Troglitazone X X X X X X
Troleandomycin X X X
Trovafloxacin X X X
Urethane X X X
Valproic acid X X X X X X X X A
Venlafaxine X X X X B
Verapamil X X X X C
Vincristine X b X X C
Vitamin A X X X X T
Warfarin X X C
Xenylamine X X
Ximelagatran X X X
Zafirlukast X X C
Zidovudine X X B
Zimelidine X
Zonisamide X X D
Zoxazolamine X X
Herbal
Barakol X X
Black cohosh X X X
Bush tea (pyrrolizidine alkaloids) X X
Cascara sagrada X
Chaparral X X X X
Chaso/Onshido X X X X
Comfrey X
Germander (teucrium) X X X
Glycyrrhizin X
Greater celandine X X X
Green-lipped mussel (Seatone) X
Jin bu huan X X X
Kava X X X
Ma huang X X
Margosa oil X
Mate tea X
Mineral oil X
Oil of cloves X X
Pennyroyal oil X X
Pentanoic acid X
Polyvinylpyrrolidone X
Prostata X
Senna X
Skullcap X
Syo-saiko-to X X X X X
Tannic acid X X
Usnic acid X

The data in this table were compiled from multiple sources. In addition to the primary literature, use was made of information in references. The patterns of pathology and biochemistry presented in this table are meant to be general guides and not absolute criteria.
d Literature documentation of idiosyncratic injury according to Bjornsson and Hoofnagle. A:50 or more published cases; B: 13 to 49 published cases; C: 4 to 12 published cases; D: 1 to 3 published cases; T: Direct toxins at high dose levels; Z: case reports of questionable causality only.
VBDS , Vanishing bile duct syndrome; VOD/SOS , veno-occlusive disease/sinusoidal-obstruction syndrome.

a Laboratory biochemical injury as defined by the ratio of alanine aminotransferase to alkaline phosphatase as described in the text.

b Only in combination with other agents or radiotherapy.

c Predominantly zone 1 necrosis.

Necroinflammatory Patterns ( Figures 23.1 to 23.8 )

It is frequently the case that patients with hepatotoxicity come to clinical attention because of the results of a necroinflammatory injury. A glance at Table 23.8 will reveal that necrosis and inflammation involving hepatocytes are probably the two most common outcomes of drug-induced liver injury. There is a huge variation in the degree of necrosis and inflammation that may be seen with any particular drug injury, from coagulative necrosis (usually zonal) with little or no inflammation to mild spotty lobular inflammation with little cell death to fulminant hepatitis with marked inflammation and nonzonal necrosis to patterns that mimic chronic viral hepatitis.

Figure 23.1, Nitrofurantoin toxicity—acute fulminant hepatitis. Nitrofurantoin has been associated with both acute and chronic liver disease. The biochemical presentation varies from pure hepatocellular to cholestatic and most of the reported cases are in women and in older individuals. Toxicity may not develop until the patient has been on the drug for several years and yet the patient may still present in fulminant hepatic failure. The histopathology mainly shows changes of hepatitis and the distribution and severity may mimic both acute and chronic viral hepatitis. Severe fibrosis and cirrhosis may be present at the time of biopsy. This patient presented with acute hepatitis and jaundice. A , The biopsy shows lobular inflammation associated with ballooning injury of hepatocytes. There is extensive hepatocyte dropout in zone 3 in this portion of the biopsy whereas other areas showed panacinar necrosis (hematoxylin and eosin [H&E], 200×). B , The infiltrate is mainly lymphocytic with scattered eosinophils and plasma cells. Hepatocellular rosettes are present. Canalicular cholestasis is not seen (H&E, 600×). C , A Masson stain in an area of panacinar necrosis shows relatively preserved portal areas with collapse of intervening parenchyma. No hepatocytes remain in this portion of the biopsy but there is a ductular reaction and persistent inflammation (Masson trichrome, 200×).

Figure 23.2, Nitrofurantoin toxicity—chronic hepatitis pattern. This case presented with moderate elevations of transaminases and a normal bilirubin. A , The distribution of inflammation observed at low power is mainly portal and periportal, mimicking chronic viral hepatitis. The lobular inflammation is relatively mild compared with the acute hepatitis presentation in Fig. 23.1 (hematoxylin and eosin [H&E], 100×). B, The portal areas show lymphoplasmacytic infiltrates with scattered eosinophils. There is interface hepatitis and the duct is uninjured (H&E, 400×). C , A feature not consistent with chronic viral hepatitis is the presence of central necrosis. Similar to the acute hepatitis presentation there is accentuation of inflammation and necrosis in zone 3 (H&E, 400×). D , Focally, bridging necrosis is present, here connecting a central vein region with a portal area. This is another feature of severity that would be unusual for chronic viral hepatitis, but more common in autoimmune hepatitis (H&E, 200×).

Figure 23.3, Advanced liver disease due to nitrofurantoin. Patients who develop nitrofurantoin toxicity may develop advanced fibrotic liver disease. This biopsy was taken about two months after the acute presentation at a time when the transaminases were only mildly elevated. A , There is clear evidence of bridging fibrosis and nodule formation consistent with at least incomplete cirrhosis. Mild to moderate lymphocytic inflammation is present with focal interface hepatitis (Masson trichrome, 100×). B , Some portal areas showed cholatestasis of the periportal hepatocytes, here associated with the absence of the bile duct (hematoxylin and eosin, 400×). C ) Copper accumulation was seen in some of the periportal hepatocytes. The chronic cholestatic features in this case may be as much because of the advanced stage of the liver disease or to drug toxicity (Rhodanine, 600× original magnification).

Figure 23.4, Isoniazid hepatitis. Isoniazid causes hepatocellular injury with jaundice in about 1% of patients. The incidence increases with age and alcohol use. Patients on more than one antituberculous agent may also be at risk of hepatotoxicity. The histologic pattern of injury varies from acute hepatitis to cholestatic hepatitis. A , This example of isoniazid injury shows diffuse lymphocytic inflammation involving portal areas and hepatic parenchyma with hepatocyte dropout. Scattered eosinophils are present, but only rare plasma cells (hematoxylin and eosin [H&E], 200×). B , At high magnification, acidophil bodies are readily identified. There is wide variation in hepatocyte cell size, consistent with regeneration (H&E, 600×). C ) In this case there is mild duct injury. The ductal epithelial cells show reactive changes, with nuclear variation and crowding. There is also a prominent ductular reaction with a neutrophilic infiltrate. No canalicular or hepatocellular cholestasis was seen in this case despite significant jaundice (H&E, 600×).

Figure 23.5, Lamotrigine toxicity. Lamotrigine is an antiepileptic drug that has recently been associated with an acute hepatitic type of hepatotoxicity. A , This biopsy from a patient with lamotrigine hepatitis shows several large foci of lobular inflammation associated with hepatocellular apoptosis. The inflammation is lymphohistiocytic with eosinophils (hematoxylin and eosin [H&E], 200×). B , The portal areas are filled by a lymphocytic infiltrate with numerous eosinophils. There is interface hepatitis present and several apoptotic hepatocytes can be seen at the edges of the portal area. The ducts are relatively unaffected by the infiltrate and there was no cholestasis visible in the biopsy (H&E, 600×).

Figure 23.6, Ciprofloxacin hepatitis. Ciprofloxacin has been associated with both hepatitic and cholestatic jaundice. In this case there is both portal and lobular inflammation, with eosinophils and plasma cells in the infiltrate. There was no cholestasis in the biopsy (hematoxylin and eosin, 400×).

Figure 23.7, Herbal-associated hepatoxicity. Hepatotoxicity due to herbal nutritional supplements has been the subject of a number of case reports and small case series. Pathology ranging from fulminant hepatitis to cholestasis to sinusoidal-obstruction syndrome has been observed. A , This biopsy was obtained from a patient with acute hepatitis due to a green tea extract. There is prominent necrosis in zone 3 associated with a predominantly lymphocytic infiltrate. There is bridging necrosis between the central vein and the adjacent portal area (hematoxylin and eosin [H&E], 100×). B, This biopsy was obtained during an episode of jaundice caused by Chaparral (beechwood creosote). There is a predominantly lobular hepatitis without cholestasis. The moderate steatosis present was most probably related to the patient’s obesity (H&E, 400×).

Figure 23.8, Zonal necrosis due to acetaminophen. Acetaminophen causes a distinctive pattern of coagulative, zonal necrosis with minimal inflammation consistent with its intrinsic toxicity. The degree of toxicity increases with increased dose, increased acetaminophen blood levels, increased cytochrome CYP2E1 activity, decreased glutathione stores, increased alcohol consumption, fasting, and obesity. A , There is coagulative necrosis of hepatocytes involving about 50% of the parenchyma (hematoxylin and eosin [H&E], 100×). B , At the interface between the viable and necrotic liver there is steatosis and ballooning of hepatocytes (H&E, 400×) (also see eSlide 1.13 ). C , In the viable areas of the liver, isolated apoptotic hepatocytes can be seen, along with mitotic figures (H&E, 600×). D , In this biopsy from a case of acetaminophen toxicity in a chronic alcoholic, the lipid vacuoles in the steatotic hepatocytes fuse to form large irregular lipid lakes (H&E, 400×).

Patterns of inflammation can be subdivided into patterns that mimic acute hepatitis, with a lobular predominance of inflammation, patterns that mimic chronic hepatitis (with or without fibrosis), and other more specific patterns, such as granulomatous hepatitis ( eSlide 19.7 ) or mononucleosis-like sinusoidal infiltrate. These distinctions are useful when formulating a differential diagnosis or in deciding how to further work up the case. It is also important to remember that all of these patterns may have a clinically acute presentation. Acute hepatitis-like injury is dominated by foci of lobular inflammation and spotty necrosis. The degree of severity may vary from a few widely scattered foci or apoptotic hepatocytes to large areas of bridging and confluent necrosis ( Figs. 23.1, 23.4 to 23.7 ; eSlide 23.1, eSlide 23.2 ). There is usually portal inflammation and interface hepatitis, sometimes severe, but the majority of the injury is in the lobule. Duct injury may be present, but cholestasis is not observed in the pure acute hepatitic drug injury. Hepatocellular changes can include ballooning and steatosis. There may be evidence of regeneration with the appearance of mitotic figures, widened hepatocyte plates, and hepatocyte rosette formation. Confluent necrosis in zone 3 is not an uncommon finding and may be the result of the toxic injury or extrahepatic causes such as shock. As the injury becomes more severe and the areas of necrosis merge, fulminant hepatitis with massive necrosis may be the result ( eSlide 23.3 ). Trichrome stains can help distinguish between recent parenchymal loss with collapse and parenchymal extinction seen in advanced cirrhosis (see Fig. 23.1C ). Unless the injury has been present for longer than clinically recognized (as in some cases of subacute toxic hepatitis) or the patient has some underlying chronic liver disease, it is rare to see more than periportal fibrosis in this pattern of drug-induced liver injury. If canalicular or hepatocellular cholestasis is present along with the acute hepatitis like pattern of injury, then the case is better classified as a mixed cholestatic and hepatocellular type (cholestatic hepatitis), which is discussed later in the section on cholestatic patterns. The acute hepatitis-like pattern is one of the most common drug induced injury patterns, comprising 21% of cases in a cohort of patients with suspected drug injury.

Drugs may also cause a pattern of injury that may be indistinguishable from chronic viral or autoimmune hepatitis on histologic grounds alone ( Figs. 23.2 and 23.3 , eSlide 23.4 ). In fact, many of the drugs associated with the acute or lobular hepatitis pattern may also be associated with the chronic or portal hepatitis pattern (see Table 23.8 ). Some common agents associated with the chronic hepatitis-like pattern include nitrofurantoin, isoniazid, and the sulfonamides. In these biopsies, there is generally portal-dominant inflammation with interface hepatitis associated with a mild to moderate degree of spotty lobular inflammation. Apoptotic hepatocytes as well as other evidence of injury such as ballooning degeneration and steatosis may be seen. As with the acute hepatitis-like injury, if canalicular or hepatocellular cholestasis is present these cases should be classified with the mixed cholestatic and hepatocellular type for the purposes of differential diagnosis. This pattern of injury tends to have lower aminotransferase elevations than the acute hepatitis forms and may go undetected for a long time. Cirrhosis may develop, as in the case of nitrofurantoin toxicity shown in Fig. 23.3 . In such cases other causes of cirrhosis should be excluded histologically and clinically.

Drugs that cause chronic hepatitis patterns may be further subdivided by whether or not they are associated with features of autoimmune hepatitis. Portal infiltrates are more likely to show plasma cells than other types of drug injury. A number of drugs, including nitrofurantoin, methyldopa, and minocycline, induce an autoimmune hepatitis that is clinically similar to sporadic type I autoimmune hepatitis and termed drug-induced chronic hepatitis, Type I. Patients frequently have circulating antinuclear and/or anti-smooth muscle antibodies, high gamma globulin levels, and plasma cell–rich infiltrates on liver biopsy. Similar to the sporadic form of autoimmune hepatitis, there is a female predominance and the onset may be acute or chronic. A second group of drugs is associated with autoantibodies directed against microsomal proteins such as isoforms of cytochrome P450 similar to Type II autoimmune hepatitis. These drugs are categorized as drug-induced chronic hepatitis Type II and include dihydralazine (anti-CYP1A2), ticrynafen (anti-CYP2C9), and halothane (anticarboxylesterase and antiprotein disulfide isomerase).

Phenytoin, dapsone, and several other agents have been associated with a pseudomononucleosis type of inflammatory pattern. There is sinusoidal beading present and both of these agents may also induce granulomas and eosinophils. Infection by Epstein-Barr virus should be excluded by serologic testing and in situ hybridization.

A large number of drugs have been associated with granulomatous inflammation (see Table 23.8 ) ( eSlide 19.7 ). The presence of microgranulomas (small collections of 3 to 10 epithelioid macrophages) in the hepatic parenchyma is a common finding in many types of chronic liver disease as well as in drug injury. They should not, by themselves, lead to a diagnosis of granulomatous hepatitis, drug-induced or otherwise. Larger epithelioid granulomas, particularly when present in significant numbers, may be a clue to drug-induced injury, particularly when sarcoidosis and infections have been excluded. They are less common, and were noted in only 5% of the DILIN cohort. In McMaster’s series of 95 cases of granulomatous hepatitis, about 30% were attributed to drugs. A wide variety of drugs were incriminated, including antihypertensives, anticonvulsants, antirheumatics, antimicrobials, antiarrhythmics, antineoplastics, anxiolytics, and contraceptives. Other authors have noted a lower incidence related to drugs, anywhere from 1% to 10%. The drugs for which granulomas are a common component of the injury include allopurinol, carbamazepine, copper sulfate, diphenylhydantoin, phenylbutazone, phenytoin, quinidine, and quinine. Granulomas in drug injury may be parenchymal, portal or periductal, mimicking the florid duct lesion of primary biliary cholangitis. Fibrin-ring granulomas have been associated with allopurinol. Eosinophils may be seen in and around drug-induced granulomas, and granulomas may be an indicator of hypersensitivity reactions.

The death of hepatocytes usually takes one of two forms, apoptosis and necrosis. Apoptosis, or single cell death, is observed in most drug-induced injuries to some degree and was documented in 78% of cases in the DILIN series. Apoptotic hepatocytes are recognized as small, shrunken, hypereosinophilic bodies with or without a condensed, fragmented nucleus. They may be found associated with clusters of inflammatory cells, adjacent to larger areas of necrosis or occasionally as free bodies in the sinusoids. In the context of drug-induced injury, apoptosis may result from selective injury to organelles that triggers the death pathway or by initiation of apoptosis by immune cells during a hypersensitivity reaction. There is usually no clear zonal distribution of apoptosis in drug injury. Idiosyncratic drug injuries are more often associated with apoptotic cell death rather than zonal necrosis. However, in severe cases of necroinflammatory drug injury, hepatocellular cell death may occur so rapidly and completely that it is no longer possible to distinguish the actual mechanism of cell death.

In contrast to apoptosis, necrosis occurs when a cell receives massive injury in a short period. This injury can result from an environmental cause, like sudden, severe hypoxia or thermal injury or by massive injury from a drug or toxin. Cell membranes and organelles are injured indiscriminately and the cell rapidly loses all internal integrity. Because the lobular architecture of the liver defines a hepatocyte’s access to blood flow and oxygen as well as the levels of detoxifying enzymes, necrosis frequently occurs in a zonal distribution. Intrinsic hepatotoxins, both direct and indirect, are often incriminated when zonal necrosis is the dominant form of injury. Zonal necrosis usually involves either zone 3 or zone 1. Zone 2 necrosis has been produced in experimental model systems of toxicity but is very rare in human drug injury. Idiosyncratic toxins may also produce zonal injury, perhaps as a result of increased susceptibility of cells in particular zones or from particularly intense perivenular or periportal inflammatory infiltrates. Zone 3 necrosis is the most common form of zonal necrosis and is the characteristic form of toxicity due to acetaminophen and carbon tetrachloride ( eSlide 23.5, eSlide 1.13 ). In the DILIN series, which exclude acetaminophen, zone 3 necrosis was evident in 15% of cases. In the case of both of these agents, there is little inflammation except for macrophages and neutrophils that have been drawn to the area secondarily. Early on after the initiation of the injury, a biopsy will show sheets of hepatocyte ghosts in a zone 3 distribution ( Fig. 23.8 ). Hemorrhage can be seen as the sinusoidal structure breaks down and steatosis may be seen in the nonnecrotic liver. The entire acinus may be involved in severe injuries. If the patient survives the initial toxic insult, the dead hepatocytes will be phagocytized and removed, leaving a zone of collapsed reticulin. With sufficient time the liver can regenerate to the point where the architecture is essentially normal. Zone 1 coagulative necrosis is rarer, but has been associated with poisoning by direct intrinsic hepatotoxins such as phosphorus, ferrous sulfate, and concentrated acetic acid. Finally, it should be remembered that zonal necrosis (particularly zone 3 necrosis) may be observed in hepatitic and vascular patterns of drug injury.

Cholestatic Patterns ( Figures 23.9 to 23.15 )

Drug injury with either bile accumulation or evidence of chronic cholestasis are common findings on biopsy, accounting for 49% of the DILIN cases. Similar to the hepatitic patterns of drug-induced liver injury, the cholestatic patterns may be subdivided into several forms that mimic acute and chronic nondrug cholestatic liver disease. On the acute side are patterns of pure intrahepatic cholestasis and mixed hepatocellular-cholestatic injury or cholestatic hepatitis (see Table 23.8 ). Acute intrahepatic cholestasis is characterized mainly by the accumulation of bile within canaliculi (canalicular cholestasis) and hepatocytes (hepatocellular cholestasis) ( Figs. 23.9 to 23.11 ). Within hepatocytes, bile may be difficult to distinguish from other hepatocellular pigments like lipofuscin and iron. Bile appears as variably sized rounded inclusions with pale green to greenish brown color. Iron stains can be very helpful by both excluding the possibility of iron and allowing the cytoplasmic pigments to be seen more clearly (see Fig. 23.9D ). The low background counterstain used in rhodanine stains is also useful for visualizing intracellular bile (see Fig. 23.10C ). Ballooning hepatocellular injury may accompany the bile stasis. Cholestasis is most prominent in zone 3, and one should exclude other processes such as sepsis and acute large duct obstruction that may also present with isolated zone 3 cholestasis. In the most pure forms of acute intrahepatic cholestasis, such as the cholestasis from androgenic or contraceptive steroids, there is little or no inflammation. In most cases of drug-induced cholestasis both hepatocellular and canalicular cholestasis are present, although the sex steroids notably produce only canalicular cholestasis. A mild degree of lobular and/or portal inflammation as well as duct injury may also be present. It is much rarer to see bile plugs in interlobular ducts or cholangioles in drug-induced cholestasis, although benoxaprofen has been reported to cause both.

Figure 23.9, Cholestatic injury due to amoxicillin-clavulanate. Patients who develop toxicity to amoxicillin-clavulanate usually present after they have completed their course of therapy. The injury is usually cholestatic and is recognized by the development of jaundice one to nine weeks after stopping the drug. Histologically, all forms of cholestatic injury have been reported, from pure intrahepatic cholestasis to mixed hepatitic/cholestatic injury to vanishing bile duct syndrome. A , Pure intrahepatic cholestasis injury shows little inflammation—usually a sparse portal infiltrate and very rare foci of spotty necrosis, leading to a nearly normal appearance at low magnification (hematoxylin and eosin [H&E], 100×). B , Careful examination reveals canalicular cholestasis ( arrow ), occasional enlarged hepatocytes with clearish, microvacuolated cytoplasm and small clusters of pigmented macrophages (H&E, 600×). C , This biopsy from a case with mixed injury shows numerous foci of spotty lobular inflammation alongside canalicular and hepatocellular cholestasis (H&E, 400×). D , Iron stains are helpful in distinguishing pigments in the liver. Bile plugs may be easier to see in an iron stain than in a standard H&E because the brownish green bile pigment contrasts well with the pale pink of the background in an iron stain (iron, 600× original magnification). E , Duct injury is frequently seen in cases of amoxicillin-clavulanate injury. In this case it took the form of primary biliary cholangitis-like florid duct lesions. The ductal epithelium is extensively infiltrate and shows a hyperplastic response. There is a prominent eosinophilic infiltrate and cholatestasis changes in the periportal hepatocytes (H&E, 400×) (also see eSlide 23.7 , eSlide 28.2 , eSlide 28.3 ).

Figure 23.10, Azithromycin toxicity. Intrahepatic cholestasis and cholestatic hepatitis are typical patterns of injury with the macrolide antibiotics. Injury has been more often reported with erythromycin than with the other members of the drug family. This case demonstrated acute intrahepatic cholestasis with loss of the small bile ducts. A , There is zone 3 cholestasis with accumulation of bile pigment mainly in hepatocytes although canalicular cholestasis is also present. This accumulation is associated with mild hepatocyte swelling and occasional hepatocyte apoptosis. There is almost no inflammatory infiltrate (hematoxylin and eosin [H&E], 400×). B, Most of the small portal areas lacked a visible bile duct, but there was no evidence of periportal cholatestasis (H&E, 400×). C, The copper stain was negative for copper accumulation, but the zone 3 bile stasis was evident as a greenish discoloration ( upper left ) (Rhodanine stain, 200×).

Figure 23.11, Cholestatic injury with duloxetine. Duloxetine has only recently been associated with hepatotoxicity with a reported case of fulminant hepatic failure. Here are two examples of cholestatic injury judged to be due to duloxetine. A , The first case shows acute intrahepatic cholestasis with very little inflammation. There is no hepatocellular dropout, but scattered pigmented macrophages are seen in the sinuses. There was only mild portal inflammation without interface hepatitis (hematoxylin and eosin [H&E], 200×). B , Under high magnification, canalicular and hepatocellular cholestasis are identified, mainly around the central veins (H&E, 600×). C , A separate case shows mixed hepatocellular and cholestatic injury, with lobular inflammation, hepatocyte dropout, and canalicular cholestasis. There is prominent Kupffer cell hypertrophy in the sinuses (pale cells between hepatocyte cords) (H&E, 400×).

Figure 23.12, Chronic cholestatic hepatitis due to cefuroxime. Cephalosporins only rarely cause hepatic injury and when they do it is often a cholestatic jaundice, as is the case in this example of injury due to cefuroxime. Overall the biopsy shows changes reminiscent of chronic autoimmune hepatitis, but with some notable and unusual features. A , The portal areas show a relatively mild lymphocytic infiltrate with prominent ductular reaction and cholatestasis (pseudoxanthomatous change) in the periportal hepatocytes. The ducts were intact although some showed injury (hematoxylin and eosin [H&E], 400×). B , The chronic cholestatic changes are corroborated by a positive copper stain (Rhodanine stain, 600×). C , In addition to the portal inflammation there is zone 3 necrosis that was associated with a prominent plasma cell infiltrate (H&E, 600×). D , A Masson trichrome stain shows areas of bridging fibrosis involving portal areas and central veins (Masson trichrome, 100×).

Figure 23.13, Fluvastatin-related cholestatic hepatitis. Statins are only very rarely causes of significant hepatic injury. Because statins are used in a patient population (hypercholesterolemics) that is at risk for fatty liver disease, these patients may have mildly elevated transaminase levels unrelated to drug therapy. This case of fluvastatin toxicity demonstrated mild mixed hepatocellular and cholestatic injury on biopsy. A , Examination of zone 3 shows canalicular cholestasis associated with mild lobular inflammation and hepatocellular apoptosis. There was also mild duct injury (hematoxylin and eosin, 600×). B , A periodic acid–Schiff (PAS) stain done with diastase digestion shows numerous small clusters of PAS-positive macrophages in zone 3 (PAS with diastase, 400×).

Figure 23.14, Trimethoprim-sulfamethoxazole–related injury. The combination drug trimethoprim-sulfamethoxazole causes a wide range of injury from nearly pure intrahepatic cholestasis to acute hepatitis, with cholestatic presentations being more common. This case shows mixed hepatocellular and cholestatic injury on a background of mild fatty liver disease, probably related to obesity. A , The inflammatory infiltrate is mild in intensity and present mainly in the portal areas. There is interface hepatitis as well as ductular reaction, both of which obscure the limiting plate (hematoxylin and eosin [H&E], 200×). B , The portal infiltrate is mainly lymphocytes, with increased numbers of eosinophils (H&E, 600×). C , Canalicular cholestasis is present throughout the lobule but is most visible in zone 3 (H&E, 600×).

Figure 23.15, Atomoxetine toxicity. Atomoxetine is a recently developed norepinephrine reuptake inhibitor used to treat attention-deficit hyperactivity disorder. Several case reports have linked it with hepatotoxicity. This biopsy was obtained in the midst of the biochemically hepatitic presentation associated with jaundice. The histologic pattern of injury is a cholestatic hepatitis with the hepatitic component being the more prominent one. A , At low magnification, there is both portal and lobular inflammation, with evidence of hepatocellular injury in the form of ballooning and hepatocyte rosette formation (hematoxylin and eosin [H&E], 200×). B , There is a mild to moderate portal inflammatory infiltrate with interface hepatitis and scattered eosinophils. This portal area had no visible duct, but ducts were present in most other portal tracts (H&E, 600×). C , In zone three there is evidence of focal hepatocyte dropout and dilated canaliculi with pale bile accumulation (H&E, 600×). D , The canalicular cholestasis is more apparent on the iron stain where it is seen as pale greenish-pink plugs in canaliculi (Iron stain, original magnification 600×).

As the degree of inflammation associated with the intrahepatic cholestasis increases, the cases are better classified as mixed hepatocellular-cholestatic injury (cholestatic hepatitis). The reason for making this distinction has more to do with the pathologic differential diagnosis than with distinctive patterns of drug injury because many drugs that cause cholestatic hepatitis are also associated with more bland forms of cholestasis or with the acute hepatitis pattern (see Table 23.7 and 23.8 ). This mixed pattern of injury is a common pattern of drug-induced liver injury, but is unusual outside that context. All cases show some degree of hepatocellular injury with inflammation of the lobules and portal areas along with zone 3 predominant canalicular and hepatocellular cholestasis ( Figs. 23.9, 23.11, 23.13 to 23.15 ; eSlide 23.6, eSlide 23.7 ). The inflammatory pattern may mimic either the acute or chronic hepatitis-like patterns described earlier. Histologic changes of acute hepatitis with cholestasis are seen in about 22% of cases of drug-associated cholestatic hepatitis. Duct injury is present in about half of cases, and with some drugs like amoxicillin-clavulanate, chlorpromazine, and trimethoprim-sulfamethoxazole, patients may develop a vanishing bile duct syndrome ( eSlide 28.2, eSlide 28.3 ).

Drugs may cause a variety of injuries that can be grouped together under the general pattern of chronic cholestasis. These include patterns of ductal paucity, often termed “vanishing bile duct syndrome,” ( eSlide 23.8 ) and injuries that mimic the more specific lesions of primary sclerosing cholangitis (biliary sclerosis) and primary biliary cholangitis . Drugs and other toxins may directly injure the cholangiocytes or the ducts may be destroyed secondarily by inflammation or ischemia. Duct injury by itself should not be taken as the characteristic lesion of chronic cholestasis, as it may be observed in the hepatitic and cholestatic patterns discussed earlier. It is more important to systematically evaluate all of the portal areas and assess the status of the main duct—intact, injured, inflamed, or missing. Cytokeratin 7 or 19 stains may be useful in identifying duct remnants obscured by inflammation. Ductular reaction may be present with duct loss, but it is not a specific finding. It is better to look for evidence of cholatestasis (see Figs. 23.9E and 23.12 ), the microvacuolar change in periportal hepatocytes that is the result of bile salt accumulation. Copper stains can also be useful markers in the evaluation of chronic cholestasis although they may also be positive in advanced-stage liver disease from all causes. Fibrosis can develop secondarily as in other chronic cholestatic liver diseases. The PSC-like injury of biliary sclerosis is a relatively unusual pattern of chronic cholestatic drug injury, associated mainly with hepatic arterial infusion of floxuridine as well as the treatment of echinococcal cysts with scolicides. The injury has been attributed to arterial damage by the agents rather than direct injury to the bile ducts. Ludwig has therefore termed this change “ischemic cholangiopathy”.

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