A46-yr-old man with a history of long-standing type 2 diabetes, hypertension, chronic atrial fibrillation, hemodialysis-requiring end-stage renal disease, and left below-the-knee amputation due to severe peripheral arterial disease presented with a 2-d history of atraumatic acute-onset and then progressively worsening right anteromedial thigh pain, which was constant, aching, and aggravated with motion. He was an ex-smoker and a social drinker, and he denied use of illicit drugs. Medications included sitagliptin, amlodipine, metoprolol, lisinopril, aspirin, simvastatin, erythropoietin, and warfarin. Physical examination was remarkable for weak distal pulses and severe tenderness, erythema, and edema of the affected thigh without paresthesia or focal weakness. He had a normocytic normochromic anemia without leukocytosis, serum creatinine of 12.4 mg/dl, normal alanine and aspartate aminotransferases, normal thyroid function, creatine kinase of 228 U/liter (normal range, 30– 200), and aldolase of 13.9 U/liter (normal range, 1.2–7.6). Blood cultures and tests for autoimmune myositis were negative. Magnetic resonance imaging showed extensive edema through the entire extent of vastus medialis (Fig. 1, A and B). A muscle biopsy was performed, which showed muscle fibers undergoing active necrosis with extensive perivascular and endomysial lymphohistiocytic infiltrate, consistent with a diagnosis of diabetic myonecrosis (Fig. 1, C and D). The patient was discharged on analgesics. Diabetic myonecrosis is a rare complication of diabetes with advanced microvasculopathy and presents most commonly with acute pain and swelling of the thigh (1). Other reported risk factors are antiphospholipid antibodies (2) and cirrhosis (3). Differential diagnosis includes pyomyositis, primary muscle lymphoma/sarcoma, necrotizing fasciitis, soft tissue abscesses, deep vein thrombosis, dermatomyositis, focal/proliferative/nodular myositis, and cellulitis (1). Pathogenesis involves muscle infarction due to arteriosclerosis or diabetic microangiopathy (4). Diabetic myonecrosis predicts a poor prognosis.
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