Diabetic Amyotrophy: A Rare but Striking Neuropathy

Here’s everything you need to know about this rare but striking neuropathy.

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A 45-year-old man, RT, with a six-month history of poorly controlled type 2 diabetes presents for evaluation of increased weakness and pain in the left lower extremity. The symptoms developed in the past three weeks. Previously able to ambulate without assistance, he purchased a cane yesterday due to concerns about falling.

RT reports poor adherence to his diabetes medications. His fingerstick blood sugars have ranged from 200 to 380 mg/dL over the past month. His weight has been stable; his BMI is 34. Review of other systems is negative. Vital signs include a blood pressure of 125/82 mm Hg; pulse, 74 beats/min; and respiratory rate, 16 breaths/min.

Physical examination is notable for muscle atrophy and tenderness to compression in the left quadriceps. Straight leg raise does not elicit pain bilaterally. Muscle strength is 4-/5 in the left hip with pain elicited on hip flexion, 4-/5 in the left knee, and 5/5 in the left ankle. Muscle strength is 4+/5 in the right hip, 5/5 in the right knee, and 5/5 in the right ankle. Muscle strength in both upper extremities is 5/5. Patellar deep tendon reflexes (DTRs) and ankle DTRs are absent bilaterally. Biceps and triceps DTRs are each 2+ bilaterally. Gait is slow and unsteady with use of the cane. Cranial nerves I-XII are intact. Sensation to sharp and dull testing is normal in both the upper and lower extremities.

Labwork reveals an A1C of 10.8%. The patient’s thyroid function studies, creatine kinase, and vitamin B12 level are all in normal range. The serum creatinine is 1.2 mg/dL, and eGFR (estimated glomerular filtration rate) is 58 mL/min/1.73 m2. Liver enzymes are normal, and complete blood count and other chemistry panels are unremarkable.

RT is referred to neurology. MRI of the thoracic and lumbar spine shows no mass lesions or disc disease. Electromyography reveals findings consistent with denervation and axonal damage in the proximal muscles in both lower extremities (left > right).

RT is diagnosed with diabetic amyotrophy and begins physical therapy three days a week. He achieves aggressive improvement in blood sugar control, and after three months, his A1C has improved to 7%. Although still using a cane, he reports improved muscle strength in the lower extremities and better gait stability.

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