How does diabetic amyotrophy present? How is it different from diabetic muscle infarction?
Diabetic amyotrophy presents with severe pain and dysesthesia involving most commonly the proximal muscles of the pelvis and thigh. The paraspinal and shoulder girdle muscles can also be involved. Onset is commonly unilateral, but spread to the contralateral leg occurs in over three-fourth patients. Anorexia, weight loss, and unsteady gait due to muscle wasting and weakness may be seen. The typical patient is a 50 to 60-year-old man with well-controlled, mild type 2 DM of several years’ duration, although it can be the presenting sign of diabetes in up to 20% of cases. Usually the patient has no evidence of diabetic retinopathy or nephropathy but may have a distal symmetric sensory neuropathy as well as signs of an autonomic neuropathy.
Laboratory evaluation is usually unremarkable except for an elevated cerebrospinal fluid protein. Electromyography (EMG)/nerve conduction velocity testing demonstrates changes compatible with a neuropathy, and muscle biopsy shows muscle fiber atrophy without an inflammatory infiltrate. The etiology is unclear but may be due to a vasculopathy affecting the lumbosacral plexus or femoral nerve. Treatment is conservative and includes pain control (including agents such as gabapentin, tricyclic antidepressants, and pregabalin) and physical therapy. Studies examining nerve biopsy specimens have shown an inflammatory infiltrate within the blood vessel wall in roughly 50% of affected patients, suggesting a potential role for immunomodulating therapy. Conflicting data exist in the literature regarding the efficacy of intravenous immunoglobulin, corticosteroids, plasmapheresis, and cyclophosphamide, with lack of randomized controlled trial data for any immunosuppressive agent. Over 50% recover within 3 to 18 months, though recovery is often incomplete. Some patients have recurrent episodes.
Diabetic muscle infarction is the spontaneous infarction of muscle. It occurs in patients with long-standing insulin-dependent diabetes with multiple other microvascular complications. Patients present with acute onset of pain and swelling of thigh or calf muscles over a period of days to weeks. Creatinine phosphokinase may be elevated. Clinical presentation, laboratory findings, and muscle magnetic resonance imaging help to rule out infection/abscess or malignancy, although an excisional biopsy may be necessary.
