Diabetes Case 2

Patient Background:

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.

Question 1

Which of the following disorders is the most likely diagnosis in this patient?

Diabetic polyneuropathy
Diabetic muscle infarction
Diabetic amyotrophy
Statin induced rhabdomyolysis
Correct Answer
Diabetic amyotrophy

The patient has the classic presentation of diabetic amyotrophy. Diabetic amyotrophy (lumbosacral plexopathy, diabetic lumbosacral radiculoplexus neuropathy) presents classically in older type 2 diabetes patients with acute onset, asymmetric, focal pain in one thigh followed by weakness, which then progresses to involve the other leg over the next several months.

Patients with diabetic amyotrophy often have unintentional weight loss and may have autonomic symptoms, with or without associated peripheral neuropathy. This often presents in patients with relatively recent onset diabetes, which is usually in fair control. The exact pathogenesis is unclear, but likely involves ischemia, metabolic, and inflammatory factors. An ischemic nonsystemic vasculitis has been hypothesized as the cause. Electrodiagnostic studies (EDS) reveal markedly reduced amplitudes of sensory nerve and compound muscle action potentials with only mild slowing of nerve conduction velocities.

The proximal distribution of the pain in this case contrasts with the distribution that characterizes diabetic polyneuropathy, in which distal symptoms are typically greater than proximal symptoms. Sensory symptoms are not prominent with chronic inflammatory demyelinating polyradiculoneuropathy.

Incorrect: The clinical picture is not characteristic of statin-induced rhabdomyolosis, and the creatine kinase (CK) levels are normal. Diagnosis is based on classic clinical presentation in a diabetes patient with supporting EDS.

Incorrect: Diabetic muscle infarction usually presents with unilateral, acute onset pain and tenderness of thigh (or calf); swelling and tenderness of the affected muscle usually occurs. CK levels are often elevated; magnetic resonance imaging (MRI) reveals increased signal on T2- weighted images.

Incorrect: Spinal disc herniation is unlikely with absence of low back pain and normal straight leg raising test, and diabetic radiculopathy can be discounted based on the normal electromyogram of the paraspinal muscles.