A 23–year–old man with no previous medical history presented to the Emergency department complaining of a 2–week history of intermittent right thigh swelling and pain. He denied any preceding trauma, insect bites, or strenuous activity. He gave a history of recent polyuria, polydipsia, polyphagia and 20 pound unintentional weight loss. He had a family history significant for diabetes mellitus. Physical examination revealed a young man with evidence of sinus tachycardia. He had a normal neurological exam, with full strength in his extremities and no sensory deficits. His right thigh was swollen and tender to palpation. He had no calf muscle tenderness or palpable cords. Distal pulses were intact. Doppler ultrasound ruled out deep venous thrombosis of the thigh. Plain films of the femur and knee were normal. Laboratory studies were notable for glucose of 596, HbA1C of 17.1. His creatinine phosphokinase level was 734. The diagnosis of diabetes mellitus type 1 was supported with a low C–peptide value of 0.3. Treatment was initiated with aggressive fluid rehydration, insulin therapy and NSAIDs for pain control. The patient ultimately underwent MRI with gadolinuim of the thigh. The scan revealed heterogeneous T2 intensity and corresponding heterogeneous enhancement affecting primarily the adductor magnus as well as the short head of the biceps femoris, consistent with diabetic myonecrosis. The patient was discharged on Insulin and an ACE inhibitor.
Diabetic myonecrosis typically presents with acute pain and swelling of the affected muscle, in the setting of poorly–controlled diabetes. The quadriceps is the most frequently affected muscle; diabetic myonecrosis may also involve the hip adductors, hamstrings and hip flexors. Diabetic myonecrosis typically occurs as a late complication of diabetes mellitus, often 10–15 years after diagnosis. This patient had long–standing poor glucose control as evidenced by his HbA1C level, however it is remarkable that myonecrosis was the initial manifestation of his diabetes. The pathogenesis of this rare condition is not clear, although thought to be due to muscle infarction as a result of diabetic microangiopathy and atherosclerosis. Diabetic myonecrosis is generally a self–limiting condition requiring conservative treatment with analgesics, bed rest and better glycemic control. Resolution of symptoms usually occurs within 2 weeks. Long term prognosis however is generally poor, as this entity occurs in the presence of uncontrolled diabetes mellitus with significant microvascular compromise.
Diabetic myonecrosis should be included in the differential diagnosis of a painful, swollen muscle, even in a newly diagnosed diabetic. In the absence of evidence of infection, antibiotics are not required.
Figure 1Coronal T1 weighted MRI image of R thigh showing heterogeneous enhancement affecting primarily the adductor magnus as well as the short head of the biceps femoris, consistent with diabetic myonecrosis
Figure 2Axial T1 weighted MRI image of R thigh post contrast showing heterogeneous enhancement affecting primarily the adductor magnus measuring roughly 7 cm × 5 cm consistent with diabetic myonecrosis.