A 75 year-old man with type 2 diabetes (T2D) for 8 years presents to the endocrinology office with pain and weakness of his thighs. He initially noted pain and weakness in his right thigh two months ago, but now has pain and weakness in both legs. He denies any back pain. He has difficulty getting up from the chair and has been using a wheelchair recently. He also reports that he has been losing weight. He currently takes glipizide 5 mg twice daily, metformin 1 g twice daily, aspirin 81 mg daily, rosuvastatin 40 mg daily, and enalapril 10 mg daily. Apart from diabetes and hypertension, he has no other known medical problems. He does not smoke or drink and is married. He denies any fever, trauma, or low back pain.
On examination, his height is 5' 9”, and his weight is 125 lb. His blood pressure is 130/80 mm Hg; his pulse is 60 beats per minute and regular. He is afebrile. He has 2/5 strength in both quadriceps and absent patellar reflexes bilaterally. No swelling, masses, or tenderness of the thigh muscles is noted, and distal pulses are normal. Straight leg raising produces no symptoms. Electrodiagnostic studies show markedly reduced amplitudes of sensory nerve and compound muscle action potentials with only mild slowing of conduction velocity in the motor fibers of femoral nerves bilaterally. Electromyogram of the paraspinal muscles is normal. His glycated hemoglobin (HbA1c) is 7.2% (normal, <5.7%); his serum creatinine is 1.0 mg/dL (normal, 0.8-1.3 mg/dL), and his creatine kinase levels are normal.