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Atypical Infections

Mycobacterial Infection In the 1950s, the atypical mycobacteria were recognized as human pathogens. They are morphologically similar to Mycobacterium tuberculosis but have different colonial characteristics. Because there is no evidence of human-to-human transmission, the atypical mycobacteria do not pose public health hazards. Etiology The mycobacterial organisms known to cause musculoskeletal system infections in humans are M. avium intracellulare–M. avium complex (found in soil, water, swine, cattle,…

HIV Infection and AIDS

Human immunodeficiency virus (HIV) infection is almost universally fatal if left untreated, leading to and being the etiologic agent of the acquired immunodeficiency syndrome (AIDS). The HIV epidemic is prevalent worldwide and is constantly evolving, being influenced by geographic, socioeconomic, and antiretroviral treatment–related factors. The Centers for Disease Control and Prevention (CDC) has published the current case definition criteria, which include three different categories of clinical…

Pediatric Infections

Introduction Musculoskeletal infections in children are relatively common occurrences. However, in the pediatric population, such infections may produce nonspecific clinical signs and symptoms and can occur in the absence of clinically apparent features, such as swelling and erythema. This diagnostic challenge is further compounded by the potential inability for a young child to assist in localizing a symptomatic region. Prompt recognition of bone and joint infectious…

Diabetic Pedal Infection

Introduction Etiology Although hematogenous spread is the most common cause of osteomyelitis in most other areas of the body, contiguous spread and direct implantation are the most common in the foot and ankle. Direct implantation can occur from puncture wounds or deep lacerations, open fractures, and surgery or injection procedures. The vast majority of osteomyelitis involving the foot and ankle in diabetic patients, however, occurs through…

Spinal Infection

Spinal Infection Etiology Spinal infection is a multicausal disease. The three most common are hematogenous spread, direct spread, and direct inoculation, which is usually iatrogenic. Arterial hematogenous spread can be due to an infectious focus anywhere in the body. This can be responsible for pyogenic and nonpyogenic infections and is the most common source of infection. It was previously believed that hematogenous spread can occur through…

Appendicular Infection

Osteomyelitis is infection of bone or bone marrow. It is usually caused by bacterial infection, less frequently by viruses and fungi and, rarely, parasites. It is subdivided into acute, subacute, and chronic stages, depending on the clinical presentation, which, in essence, reflects the interaction between the causative organism and the host's response ( Fig. 65-1 ). Despite the tremendous advancement in the imaging of bone infection,…

Soft Tissue Infection: Cellulitis, Pyomyositis, Abscess, Septic Arthritis

Infections of the soft tissues range clinically from indolent, low-grade conditions to fulminant disease that may be life-threatening within a matter of hours. A wide range of organisms can produce an infection, although there are common culprits. Clinical confusion may occur because the presentation may mimic tumor or degenerative disease and vice versa. Infection should always be in the mind of those involved in the diagnosis…

Noninflammatory Intraarticular Pathology

Pigmented Villonodular Synovitis Introduction Etiology Pigmented villonodular synovitis (PVNS) is a benign proliferative synovial disorder that can occur in a diffuse or localized form and in both intraarticular and extraarticular locations. Although PVNS typically occurs diffusely within a joint, nodular forms exist and, when present, are commonly referred to as localized nodular synovitis. Extra-articular PVNS can involve tendon sheaths or bursae. Localized nodular synovitis of tendon…

Neuropathic Osteoarthropathy

Neuropathy results from functional abnormalities or structural insults to the axons (sensory, motor, or combined), the myelin, or both. The insensate neuropathic joint is liable to arthrosis, fractures, alignment deformities, abnormal function, ulcer, and infection. Predilection for skeletal location is influenced by whether the insult is central or peripheral and the degree to which sensory, motor, and/or autonomic function is insulted. Because diabetic pedal neuroarthropathy (Charcot…

Crystal-Related Arthritis

A number of crystals are associated with joint disease ( Fig. 61-1 ). The major culprits are calcium pyrophosphate dihydrate (CPPD) and hydroxyapatite (HA), a basic calcium phosphate (BCP). The focus in this chapter is on the disorders associated with crystal deposition in and around joints, except for true gout, which is discussed in Chapter 60 . Open full size image FIGURE 61–1 Example of crystals…

Gout

Etiology Gout is a disease with manifestations relating directly from the deposition of monosodium urate monohydrate crystals or uric acid from hyperuricemic body fluids. In humans, urate is a nonmetabolized byproduct of purine metabolism and is excreted via the kidneys (two thirds) and gastrointestinal tract (one third). The development of gout is related to both polygenic inheritance (specifically, the inability of one's kidneys to increase urate…

Diffuse Idiopathic Skeletal Hyperostosis and Ossification of the Posterior Longitudinal Ligament

Diffuse idiopathic skeletal hyperostosis (DISH), a term proposed by Resnick is the widely accepted name describing a common disorder affecting mostly elderly persons and characterized by increased bone formation at multiple sites in the spine and peripheral skeleton. Although the radiographic changes of DISH may be florid, clinical symptoms are often mild or absent, therefore the importance of the imaging appearance in establishing this diagnosis. Ossification…

Ochronosis

Etiology Ochronosis is the bluish-black discoloration that can be seen in connective tissues of patients with alkaptonuria, a rare disorder caused by the absence of homogentisic acid (HGA) oxidase. The absence of this enzyme causes a buildup of HGA in connective tissues, including the sclera, cornea, articular cartilage, intervertebral disks, tendons, and ligaments. The accumulated HGA is polymerized and oxidized, causing the characteristic pigmentation of the…

Hemochromatosis

Hemochromatosis was first described by French physician Armand Trousseau in 1865. The major finding was the presence of a triad associating cirrhosis and diabetes in a tanned man. Von Recklinghausen reported, in 1889, the presence of strong iron deposits within the liver of those patients, therefore leading him to evoke the role of iron excess in the disease occurrence. He named the disease haemochromatosis. Etiology and…

Idiopathic Inflammatory Myopathy

Introduction Etiology The idiopathic inflammatory myopathies (IIMs) include polymyositis (PM), dermatomyositis (DM), and sporadic inclusion body myositis (sIBM). The IIMs are thought to be systemic autoimmune disorders, although a specific autoantigen has not been identified. DM is a complement mediated microangiopathy that is also mediated by plasmacytoid dendritic cells, whereas PM and sIBM are T cell–mediated disorders. Autoantibodies are often present in DM and polymyositis (PM)…

Juvenile Idiopathic Arthritis

Etiology Juvenile idiopathic arthritis (JIA) represents a heterogeneous group of autoimmune disorders that begin in childhood and involve persistent inflammation of one or more joints. Juvenile idiopathic arthritis is an umbrella term for all chronic childhood arthropathies and can be classified into seven subtypes on the basis of features present in the first 6 months of disease. The subtypes include the following: 1. Systemic onset JIA—Patients…

Mixed Connective Tissue Disease

Etiology, Epidemiology, and Prevalence The distinctiveness of the connective tissue diseases is less pronounced than the classification system implies. In practice, there is a continuous spectrum of symptom combinations, merging features of various entities. Mixed connective tissue disease (MCTD) is the prototype of an overlap syndrome, combining features of systemic lupus erythematosus (SLE), systemic scleroderma (SSc), polymyositis (PM), and rheumatoid arthritis (RA). As described by Sharp…

Systemic Lupus Erythematosus

Etiology Despite the explosion of molecular genetic research in the past decades, the etiology of this prototype autoimmune disease is still elusive. A confusing complexity of serologic, immunopathologic, and genetic phenomena has been described, most of which are likely to be secondary effects. The current main hypothesis for the initiation of autoimmune response proposes a defect in the clearance of apoptotic cells (cells undergoing programmed cell…

Progressive Scleroderma

Etiology Progressive scleroderma (also known as progressive systemic sclerosis [PSS] ) is one of the collagen vascular diseases, which makes it one of the systemic autoimmune disorders. Collagen vascular diseases include the following: PSS (progressive scleroderma) Systemic lupus erythematosus Polymyositis and dermatomyositis Sjögren syndrome Jo-1 syndrome Mixed connective tissue disease (Sharp's syndrome) Undifferentiated inflammatory systemic connective tissue disease Relapsing polychondritis These diseases have in common a…

Ankylosing Spondylitis

Clinical Presentation Ankylosing spondylitis (AS) is the prototype of the seronegative spondyloarthropathies, a moderately heterogeneous group of distinct entities composed of AS, psoriatic spondyloarthropathy, reactive spondyloarthropathy (Reiter syndrome), enteropathic spondyloarthropathy in Crohn disease and ulcerative colitis, and so-called undifferentiated spondyloarthropathy. As such, it shares several characteristics with the latter diseases: the genetic background (HLA-B27), the promotion by genitourinary or gastrointestinal bacterial infection and its subsequent or…