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Hydrostatic Pulmonary Edema

Etiology Pulmonary edema is defined as an abnormal accumulation of fluid in the extravascular compartments (interstitial and airspace) of the lung. Traditionally, pulmonary edema has been divided into hydrostatic edema and permeability edema based on the presumed mechanism. Hydrostatic edema is caused by an elevation in pulmonary capillary pressure, and permeability edema is caused by disruption of the capillary endothelium, resulting in protein leakage into the…

Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is defined as a mean pulmonary arterial pressure of greater than 25 mm Hg at rest or 30 mm Hg with exercise, with an elevated pulmonary vascular resistance (PVR) greater than 3 Wood units. Although pulmonary pressures may be elevated in many conditions, PAH fundamentally requires changes in the pulmonary vasculature. Mean pressures of 26 to 40 mm Hg are considered mild; 41 to 55 mm…

Nonthrombotic Pulmonary Embolism *

Fat Embolism Etiology, Prevalence, and Epidemiology The term fat embolism refers to the presence of globules of free fat within the pulmonary vasculature. Fat embolism is common among trauma patients, especially those with long bone or pelvic fractures. In the context of trauma, fat embolism is also common after extensive injury to subcutaneous fat, such as occurs in severe beatings or liposuction. Fat embolism must be…

Chronic Pulmonary Thromboembolism

Etiology Chronic pulmonary thromboembolism is an uncommon entity resulting from an incomplete resolution of thrombi, leading to complex restructuring processes within pulmonary arteries. Extensive clinical experience from the literature suggests that failure of thromboembolic resolution after a single embolic event or after recurrent thromboembolic events represents the predisposing condition in most patients with the disease. Although the clinical signs and symptoms are nonspecific, a confident diagnosis…

Acute Pulmonary Embolism

Etiology Pulmonary embolism (PE) refers to blood clot(s) within the pulmonary arterial system, usually caused by migration of deep vein thrombosis (DVT) from the lower extremities. Rarely, emboli are from other sources, such as the iliac veins, renal veins, inferior vena cava, right heart chambers, or upper extremity veins. More recently, there are speculations of PE developing de novo. Risk factors for PE are the same…

Takayasu Arteritis

Etiology, Prevalence, and Epidemiology Takayasu arteritis, also known as pulseless disease or Martorell syndrome, is an idiopathic chronic granulomatous arteritis affecting medium and large arteries with a predilection for the aorta and its main branches. It is seen most commonly in Japan, Southeast Asia, India, Mexico, and Brazil. Although it occurs most commonly in girls and women from eastern Asia, it has been recognized worldwide in…

Behçet Disease

Etiology, Prevalence, and Epidemiology Behçet disease is an uncommon systemic disorder of unknown etiology characterized by vasculitis and the triad of recurrent ulcers of the oral and genital mucosa with relapsing uveitis. Vascular complications develop in 20% to 40% of patients with Behçet disease and include subcutaneous thrombophlebitis, deep venous thrombosis, and pulmonary and systemic arterial aneurysms and occlusions. The reported frequency of pulmonary complications is…

Goodpasture Syndrome (Anti–Basement Membrane Antibody Disease)

Etiology, Prevalence, and Epidemiology Goodpasture syndrome, also known as anti–basement membrane antibody disease, is an autoimmune disorder characterized by repeated episodes of pulmonary hemorrhage, usually associated with glomerulonephritis and the presence of anti–glomerular basement membrane (anti-GBM) antibodies. Goodpasture syndrome is rare, with an incidence of approximately one patient per million population per year. It has a bimodal distribution with respect to age, with peaks at 20…

Antineutrophil Cytoplasmic Antibody–Associated Vasculitis

Etiology, Prevalence, and Epidemiology Pulmonary vasculitis is traditionally characterized by size of vessel involvement as defined by the Chapel Hill nomenclature. Within the small-vessel vasculitides, antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis represents a diverse group of entities, and although the inciting stimulus has not been fully elucidated, an immune-mediated response is implicated. Although rare, with an overall incidence of 20 to 100 cases per million and a…

Interstitial Pneumonia With Autoimmune Features

Interstitial pneumonia with autoimmune features (IPAF) refers to the clinical entity of interstitial lung disease (ILD) in patients with features of autoimmunity but without overt connective tissue disease (CTD). IPAF was introduced in 2015 by an international consensus panel in an attempt to standardize the nomenclature and diagnostic criteria for this entity, which represents an intermediary on the spectrum between the idiopathic interstitial pneumonias (IIPs) and…

Mixed Connective Tissue Disease

Etiology Mixed connective tissue disease (MCTD) is a disease with certain features of polymyositis, scleroderma, and systemic lupus erythematosus. Much of the evidence that MCTD is a distinct clinical entity stems from the identification of antiribonucleoprotein (anti-RNP) antibody, disease-specific human leukocyte antigen (HLA) profiles, suggestive clinical features, and because in the vast majority of patients, MCTD does not evolve into other connective tissue disease–related entities. The…

Sjögren Syndrome

Etiology Sjögren's syndrome, or “sicca syndrome,” is a disorder of the immune system that is largely defined by its two most common symptoms—dry eyes and a dry mouth; these symptoms frequently accompany other autoimmune disorders. Distinction is usually made between Sjögren’s syndrome that occurs in the absence of an accompanying connective tissue disease (primary Sjögren’s syndrome) and Sjögren’s syndrome accompanied by another connective tissue disease (secondary…

Polymyositis/Dermatomyositis

Etiology Immune-mediated muscle inflammation and vascular damage are the hallmarks of polymyositis (PM) and dermatomyositis (DM). In PM the immune system is primed to act against muscle antigens, whereas in DM there is complement-mediated damage to both endomysial vessels and the microvasculature of the dermis. The trigger for the autoimmune malfunction in PM/DM is unknown. As with other connective tissue diseases, B-cell and T-cell autoregulation is…

Systemic Lupus Erythematosus

Etiology The pathogenesis of systemic lupus erythematosus (SLE) involves genetic and environmental factors, hormonal influences, and cell-mediated responses. In SLE, B lymphocytes lose self-tolerance and inappropriately produce autoantibodies. Serologic positivity for antinuclear antibodies (ANAs) is found in nearly all patients, but anti–deoxyribonucleic acid (DNA) antibodies, although less frequent than ANAs, are far more specific for SLE. A high titer of anti–double-stranded DNA (dsDNA) is considered the…

Systemic Sclerosis (Scleroderma)

Etiology Systemic sclerosis (scleroderma) has three cardinal features: excessive collagen production, vascular damage, and inflammation The pathogenesis of systemic sclerosis is obscure, but there are several contributing factors, including genetic, environmental, and autoimmune influences. Familial aggregation for systemic sclerosis, although infrequent (1.2%–1.5% of families), has been established and lays a firmer foundation for genetic studies of its etiopathogenesis. Systemic sclerosis is considered to be an autoimmune…

Rheumatoid Arthritis

Etiology Rheumatoid arthritis (RA) is an autoimmune disorder of unknown cause with variable clinical manifestations. Genetic factors play a major role in disease susceptibility and expression. The B lymphocyte is important in the pathogenesis of RA, and therapeutic B-cell depletion has been shown to be beneficial in active RA. The exact trigger for autoantibody formation is unknown, but in animal models, both B cells and non–B-cell…

Metabolic and Storage Lung Diseases

Metabolic and storage lung diseases are a broad group of diseases and syndromes characterized by underlying biochemical or metabolic dysfunctions. Accurate diagnosis is difficult because these diseases are often indolent, are rarely encountered in clinical practice, and because their manifestations are often vague and nonspecific. These groups of disorders may affect the lung solely or as part of a systemic disorder. Metabolic Pulmonary Diseases Pulmonary Alveolar…

Eosinophilic Lung Diseases

Eosinophilic diseases of the lung include a heterogeneous group of pulmonary disorders that characteristically feature peripheral or tissue eosinophilia. Patients with these illnesses have a variable clinical presentation and may be asymptomatic or may exhibit organ dysfunction or clinical symptoms of severe respiratory illness. Histologically, eosinophilic lung diseases demonstrate infiltration of eosinophils in the pulmonary interstitium and alveolar spaces with preservation of the lung architecture. As…

Idiopathic Pleuroparenchymal Fibroelastosis

Amitani and colleagues first described a unique pattern of upper lobe–predominant, idiopathic pulmonary fibrosis (IPF) in 13 patients in the Japanese literature in 1992. The currently preferred term in the English-language literature, idiopathic pleuroparenchymal fibroelastosis (iPPFE), was coined by Frankel and colleagues in 2004 in a case series of five patients presenting with unique clinical and radiographic findings distinct from any of the previously characterized idiopathic…

Lymphangioleiomyomatosis and Tuberous Sclerosis

Etiology Lymphangioleiomyomatosis (LAM) is a systemic disease of unknown etiology, affecting almost exclusively women. LAM is characterized by idiosyncratic smooth muscle cell proliferation (LAM cells), which leads to lung cysts, systemic lymphatic abnormalities, and abdominal tumors. The main manifestation is a progressive destructive process of the lungs, which may result in respiratory failure. LAM cells can be isolated from peripheral blood, indicating the ability to spread…