Diabetic Myonecrosis Occurring in a Patient with Tight Glycemic Control

Diabetic myonecrosis is a rare and underreported complication of long-standing and poorly controlled diabetes mellitus.  Cases of diabetic myonecrosis in the setting of well controlled hyperglycemia are unusual.  We report a case of diabetic myonecrosis in a patient with relatively short duration of diabetes and tight glycemic control. 

A 57-year-old woman with Type 2 diabetes of six years duration complicated by lower extremity sensory neuropathy presented with acute right calf pain.  Hyperglycemia was managed with a basal/bolus insulin regimen and metformin; hemoglobin A1c (HbA1c) was 6.0% at time of evaluation.  In the year before hospital admission, HbA1c ranged from 6.0-7.4%.  The patient was afebrile, and examination revealed swelling, erythema, and pain of the right posteromedial calf.  No fluctuance was appreciated.  Laboratory evaluation revealed mild leukocytosis (10.5 k/mm³, 3.4-9.4) and elevations of erythrocyte sedimentation rate (50 mm/hr, 0-30) and C-reactive protein (20 mg/L, 0-5).  Magnetic resonance imaging (MRI) showed a focal lesion in the medial head of the gastrocnemius muscle measuring 2.2 x 2.4 x 3.8 cm with abnormal T2 signal concerning for neoplasm. Biopsy was performed, and histology showed inflammation and necrosis consistent with myonecrosis. Blood cultures and tissue cultures for bacteria, fungi and acid fast bacilli were negative. The patient was managed with insulin, analgesics, and empiric antibiotics, and she was discharged home after a five day hospital stay. 

Diabetic myonecrosis is a rare diabetes complication that responds well to conservative management. Risk factors for diabetic myonecrosis include long standing diabetes (typically over 10 years), poor glycemic control, and microvascular complications (most commonly nephropathy).  Women are more likely to be affected than men, and patients usually have Type 1 diabetes.  Thigh muscles are the most common site of involvement, though cases involving calf muscles are reported.  The pathogenesis of diabetic myonecrosis remains unknown.  Differential diagnosis includes pyomyositis, necrotizing fasciitis, soft tissue abscess, cellulitis, deep vein thrombosis, and hematoma.  This case is unusual in that the patient had a sustained period of good glycemic control before myonecrosis and illustrates that diabetic myonecrosis should be considered in the evaluation of well-controlled diabetic patients with acute onset, severe muscle pain.