Rheumatology Q19

Answer & Critique

Correct Answer: D

Educational Objective: Diagnose polyarteritis nodosa.

Key Point

Polyarteritis nodosa is a vasculitis affecting medium-sized arteries and is characterized by constitutional and neurologic symptoms, skin rashes, and kidney involvement that is renovascular rather than glomerular in origin.

The most likely diagnosis is polyarteritis nodosa (PAN), a vasculitis affecting medium-sized arteries. This entity may occur in the setting of chronic hepatitis B virus infection, HIV infection, and hairy cell leukemia. The most common symptoms are constitutional, including fever, malaise, and weight loss, and neurologic symptoms such as mononeuritis multiplex. Skin rashes, including purpura and necrotic ulcers, occur in more than half of patients. Kidney involvement manifests as hypertension due to renal artery vasculitis with renal infarction, not glomerulonephritis. Orchitis, an uncommon manifestation, is usually unilateral and due to testicular artery involvement. Mesenteric vasculitis may cause abdominal pain, perforation, and bleeding. This patient has all of these findings except for mesenteric involvement. Diagnosis of PAN is best established by demonstrating necrotizing arteritis in biopsy specimens or finding characteristic medium-sized artery aneurysms and stenoses on imaging studies of the mesenteric or renal arteries. This patient's renal angiogram confirms the presence of vasculitis and skin biopsy confirms medium-vessel vasculitis, consistent with the diagnosis of PAN.

Giant cell arteritis causes myalgia and elevated erythrocyte sedimentation rate but involves large vessels usually in the head and neck area or great vessels of the chest, not medium-sized vessels. Furthermore, it usually does not involve nerves or kidneys.

IgA vasculitis can cause testicular involvement, mononeuritis, and rash (palpable purpura), but it affects small vessels and causes glomerulonephritis rather than renovascular involvement.

Microscopic polyangiitis (MPA) is an ANCA-associated vasculitis affecting small vessels. It can cause neurologic involvement and skin rash, but kidney involvement is due to glomerulonephritis rather than renal artery vasculitis. Furthermore, MPA is associated with a positive ANCA with perinuclear pattern, directed against myeloperoxidase. This patient does not have a positive ANCA or glomerulonephritis, making MPA an unlikely diagnosis.

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