Aside from the usual suspects associated with a painful extremity (eg, trauma, deep venous thrombosis and soft tissue infections), think of spontaneous diabetic myonecrosis (DMN), also known as diabetic muscle infarction (1-3).
DMN is characterized by abrupt onset of painful swelling of the affected muscle, most often of the lower extremities, but also occasionally upper extremities. DMN occurs in patients with longstanding DM whose blood glucose control has deteriorated over time, often with nephropathy, retinopathy and/or neuropathy (1-3).
Couple of things to remember when considering DMN in your differential of a painful extremity. First, except for localized edema and tenderness over the involved muscle, the exam may be unremarkable. Specifically, there is no erythema or signs of compartment syndrome and fever is absent in the great majority of patients (~90%) (2). Even white blood cell count and creatine kinase (CK) are usually normal. The reason for normal CK at presentation is not clear but CK might have already peaked by the time of patient presentation (3). In contrast, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are usually elevated (>80%) (1).
MRI (without contrast in patients with renal insufficiency) is the imaging of choice with muscle enlargement and edema with hyperintense signal on T2-weighted images and other changes, including perifascial, perimuscular and or subcutaneous edema (1-3). Muscle biopsy is not currently recommended because of its adverse impact on time to symptomatic improvement. Non-surgical therapy, with rest, analgesia and glycemic control is usually recommended (1-3).
Though its exact cause is still unclear, atherosclerosis, diabetic microangiopathy, vasculitis with thrombosis and ischemia-reperfusion injury have been posited as potential precipitants for DMN. The role of anti-phospholipid syndrome, particularly in patients with type I DM, is unclear (1,2).
Bonus pearl: Did you know that symptoms of DMN may last for weeks with at least one-third of patients having a recurrence in the same muscle or elsewhere (1)?
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Reference
1. Horton WB, Taylor JS, Ragland TJ, et al. Diabetic muscle infarction: a systematic review. BMJ Open Diabetes Research and Care 2015;3:e000082.
2. Trujillo-Santos AJ. Diabetic muscle infarction. An underdiagnosed complication of long-standing diabetes. Diabetes Care 2003;26:211-15.
3. Diabetes muscle infarction in end-stage renal disease:A scoping review on epidemiology, diagnosis and treatment. World J Nephrol 2018;7:58-64.
