A 17-year-old boy comes to the office due to a skin rash that has been present for a day. One week ago, he had a sore throat that improved with oral penicillin therapy. Skin examination shows several violaceous, raised, nonblanchable lesions distributed over the bilateral lower extremities. Histologic findings of the biopsied rash are shown in the image below. Which of the following is the most likely diagnosis in this patient?

Question

A 17-year-old boy comes to the office due to a skin rash that has been present for a day.  One week ago, he had a sore throat that improved with oral penicillin therapy.  Skin examination shows several violaceous, raised, nonblanchable lesions distributed over the bilateral lower extremities.  Histologic findings of the biopsied rash are shown in the image below.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

Cutaneous small vessel vasculitis is a vasculitis that only affects the skin and typically arises due to drug or pathogen exposure (eg, hepatitis B or C virus). Drugs known to cause this condition include penicillins, cephalosporins, sulfonamides, phenytoin, and allopurinol. On skin examination, nonblanching palpable purpura is usually present and often involves the lower extremities. When biopsied, these skin lesions histologically demonstrate markedly inflamed small blood vessels with fibrinoid necrosis. In the first 24 hours, the perivascular inflammatory cell population consists primarily of neutrophils and fragmented neutrophilic nuclei (leukocytoclastic vasculitis), with mononuclear cells predominating in older lesions. (Choice A) Erythema nodosum is a form of panniculitis (inflammation of subcutaneous fat) that typically presents with painful erythematous nodules in the lower extremities. Histopathologic findings include widening of connective tissue septae due to neutrophilic infiltration and fibrin exudation, followed by histiocyte and giant cell infiltration with septal fibrosis. (Choice B) Giant cell vasculitis (temporal arteritis) affects medium- and large-sized arteries and typically presents with unilateral headache and jaw claudication in individuals age >50. Histopathologic findings include focal granulomatous inflammation of the media and internal elastic lamina fragmentation. (Choice D) Polyarteritis nodosa is a transmural, necrotizing vasculitis that affects small- and medium-sized arteries. Patients typically present with systemic symptoms (eg, fatigue, fever, weight loss), renal failure, and abdominal pain/bloody stools due to ischemia of the involved organs. (Choice E) Subcutaneous rheumatoid nodules appear as round, firm, nontender lesions that typically arise at pressure points (eg, olecranon process) in patients with advanced rheumatoid arthritis. Classic histopathologic findings include a necrotic center surrounded by palisading macrophages and lymphocytes. (Choice F) Urticaria is often caused by medications; however, patients typically develop transient erythematous, raised, blanchable skin lesions. Histopathologic findings typically include superficial dermal edema with a mild perivascular infiltrate (rare neutrophils) and dilated lymphatic channels. Educational objective: Cutaneous small vessel vasculitis is associated with medication (eg, penicillins, cephalosporins) use and typically presents with palpable purpura in the lower extremities. Characteristic histopathologic findings include marked perivascular inflammation of small blood vessels with fibrinoid necrosis and a predominance of neutrophils and fragmented neutrophilic nuclei (leukocytoclastic vasculitis). __________ References: The histological assessment of cutaneous vasculitis. (http://www.ncbi.nlm.nih.gov/pubmed/20055902)

A 17-Year-Old Boy Comes to the Office Due to a Skin