Rheumatology · Systemic Vasculitis
The facts most likely to be tested
Polyarteritis nodosa is a systemic necrotizing vasculitis that characteristically involves medium-sized muscular arteries while sparing the pulmonary circulation.
The disease is strongly associated with Hepatitis B virus (HBV) infection, which acts as a trigger for immune complex deposition in vessel walls.
Clinical presentation frequently includes renal involvement manifesting as hypertension due to renal artery stenosis rather than glomerulonephritis.
Patients often present with mononeuritis multiplex, characterized by painful, asymmetric peripheral neuropathy involving multiple nerve distributions.
Gastrointestinal involvement is common and may present as postprandial abdominal pain due to mesenteric ischemia or potential bowel perforation.
The gold standard for diagnosis is angiography showing microaneurysms and beading of medium-sized arteries, or a tissue biopsy demonstrating transmural inflammation.
First-line treatment for severe disease involves high-dose corticosteroids and cyclophosphamide, while HBV-associated cases require antiviral therapy and plasmapheresis.
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A 45-year-old male presents with a 3-week history of fever, fatigue, and weight loss. He reports severe calf pain and foot drop on the right side. Physical exam reveals livedo reticularis on the lower extremities and a blood pressure of 165/95 mmHg. Laboratory studies are significant for elevated ESR, anemia of chronic disease, and a positive Hepatitis B surface antigen.
What is the most likely diagnosis?
Polyarteritis nodosa
The patient's presentation of systemic symptoms, mononeuritis multiplex (foot drop), hypertension, and livedo reticularis in the setting of Hepatitis B infection is classic for polyarteritis nodosa.
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High yield triage
Etiology / Epidemiology
Systemic necrotizing vasculitis of medium-sized arteries; strongly associated with Hepatitis B infection.
Clinical Manifestations
Classic mononeuritis multiplex, livedo reticularis, and renal hypertension due to renal artery involvement.
Diagnosis
Tissue biopsy or angiography showing microaneurysms; ANCA-negative status is a key differentiator.
Treatment
Corticosteroids are first-line; add cyclophosphamide for severe or refractory disease.
Prognosis
Untreated disease is fatal; 5-year survival improves significantly with immunosuppression.
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Epidemiology & Etiology
Primarily affects adults aged 40-60, with a male predominance. Approximately 10-30% of cases are linked to chronic Hepatitis B virus infection. It is a systemic vasculitis that spares the pulmonary circulation.
Pertinent Anatomy
Affects medium-sized muscular arteries. It characteristically involves the renal, mesenteric, and peripheral nerve arteries while sparing the lungs.
Pathophysiology
Immune complex-mediated vessel wall inflammation leads to fibrinoid necrosis. This damage causes the formation of microaneurysms and luminal narrowing. Ischemia and infarction of downstream tissues follow the resulting vessel occlusion.
Clinical Manifestations
Patients present with constitutional symptoms like fever and weight loss. Mononeuritis multiplex (asymmetric peripheral neuropathy) is highly suggestive. Look for livedo reticularis, tender subcutaneous nodules, and hypertensive crisis from renal artery stenosis.
Diagnosis
The gold standard is tissue biopsy of affected organs or angiography demonstrating characteristic microaneurysms in renal or mesenteric vessels. Labs show elevated ESR/CRP but are notably ANCA-negative. Avoid renal biopsy if possible due to risk of hemorrhage from microaneurysms.
Treatment
Initiate corticosteroids (prednisone) for mild disease. For severe, organ-threatening, or refractory cases, add cyclophosphamide. Cyclophosphamide requires monitoring for hemorrhagic cystitis and bladder cancer.
Prognosis
Without treatment, the disease is fatal due to organ infarction or rupture of microaneurysms. With aggressive immunosuppression, the 5-year survival rate exceeds 80%.
Differential Diagnosis
Granulomatosis with polyangiitis: ANCA-positive and involves the lungs
Microscopic polyangiitis: ANCA-positive and involves capillaries/venules
Kawasaki disease: Affects children and involves coronary arteries
Cryoglobulinemic vasculitis: Associated with Hepatitis C and palpable purpura
Systemic Lupus Erythematosus: Positive ANA and multi-system involvement