Polyarteritis Nodosa – Top USMLE Diseases

Erythema nodosum is an immune-mediated panniculitis (inflammation of the subcutaneous fat) caused by a type IV (delayed-type) hypersensitivity reaction. It commonly manifests in young women as tender, erythematous nodules on the shins. The underlying etiology varies and may be associated with infection, drug exposure, inflammatory bowel disease, pregnancy, or malignancy. The lesions often self-resolve within 8 weeks without scarring. Management focuses on identifying and treating the underlying cause.

Deep vein thrombosis (DVT) is a blood clot in the deep veins, usually in the lower extremities (though they can occur in the upper extremities, mesenteric, and cerebral veins as well). The affected veins commonly include the popliteal, femoral,  iliac, and pelvic veins. The 3 primary factors (known as the Virchow triad) that contribute to DVT formation include: venous stasis, hypercoagulability, and vascular endothelial damage. Any condition that worsens 1 (or more) of these 3 factors increases the risk of DVT formation. Individuals can present with unilateral extremity pain, swelling, and/or redness around the DVT; however, a majority of cases are asymptomatic. Ultrasound can visualize the thrombus. Anticoagulation is the primary mode of treatment; the main objective is preventing a pulmonary embolism (PE).

Polyarteritis nodosa (PAN) is a necrotizing, systemic, primarily medium-vessel vasculitis. Most cases of PAN are idiopathic. Etiologic factors in secondary PAN are hepatitis B and C infection and hairy cell leukemia. PAN presents with systemic symptoms and signs such as fatigue, weight loss, fever, weakness, arthralgias, hypertension, and limb edema. Because it is a multisystem disease affecting the skin, nerves, muscles, kidneys, and blood vessels supplying the heart and GI tract, the clinical presentation depends on the organs involved. A diagnosis is made based on the history, physical examination, and laboratory test results and confirmed by biopsy or angiography. Management depends on the severity and extent of the disease. The primary treatment method is with oral glucocorticoids; immunosuppressive agents may also be needed for patients with moderate-to-severe disease.

Granulomatosis with polyangiitis (GPA) is a rare autoimmune disease of unknown etiology. It leads to a necrotizing granulomatous inflammation of small and medium-sized blood vessels of the nose, sinuses, throat, lungs, and kidneys. Early stages of GPA often present with localized manifestations such as infections of the upper respiratory tract, skin lesions, and/or constitutional symptoms. Later stages can present with renal failure and severe respiratory disease. Early diagnosis and treatment of granulomatosis with polyangiitis (which involves the administration of corticosteroids and immunosuppressive agents such as methotrexate) may lead to a full remission but without treatment, the condition has a high mortality rate.

Vasculitides are a group of conditions characterized by vasculitis, ischemia, and damage to the organs supplied by the affected vessels. The affected arteries are of different sizes and locations and vary by the type of vasculitis. Vasculitides can be a primary condition or secondary to another underlying disease. There is no clearly known pathophysiology. The diagnosis should be considered in any individual with palpable purpura, pulmonary infiltrates, ischemic events, and multisystem disease. Prompt recognition and therapy of the vasculitides are imperative, as they are often serious and sometimes fatal diseases. Management includes immunosuppressive, antiviral, and/or antiinflammatory agents.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) includes granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). All 3 diseases cause life-threatening small-vessel vasculitis with a wide range of systemic manifestations, which can involve the lungs, kidneys, skin, and heart. Diagnosis is suspected by clinical presentation and a positive cytoplasmic (c)- or perinuclear (p)-ANCA test. Biopsy of involved tissue confirms the diagnosis. Glucocorticoids and immunosuppressive therapy are the mainstays of treatment.

Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. It manifests itself as vessel stenosis and a source of thromboembolic disease. Its clinical manifestations depend on the specific vessels affected and include most notably coronary artery disease, carotid disease, and peripheral vascular disease. It is the most common primary disease of the arterial vascular system and is responsible for coronary heart disease, the leading cause of death worldwide.

Deep vein thrombosis (DVT) usually occurs in the deep veins of the lower extremities. The affected veins include the femoral, popliteal, iliofemoral, and pelvic veins. Proximal DVT is more likely to cause a pulmonary embolism (PE) and is generally considered more serious. Ultrasound can visualize the thrombus and anticoagulation is the primary mode of treatment; the main objective is the prevention of development of a PE.

Erythema nodosum is an immune-mediated panniculitis (inflammation of the subcutaneous fat) caused by a type IV (delayed-type) hypersensitivity reaction. It commonly manifests in young women as tender, erythematous nodules on the shins. The underlying etiology varies and may be associated with infection, drug exposure, irritable bowel disease, pregnancy, or malignancy. The lesions often self-resolve within 8 weeks without scarring. Management focuses on identifying and treating the underlying cause.