Clinical Reasoning: A 34-year-old woman with recurrent bouts of acral paresthesias

A 34-year-old, previously healthy woman presented with a 3-year history of persistent numbness and tingling in her feet ascending to the knees. She was a lifelong long-distance runner, and she normally experiences numbness and tingling in both feet while running that resolve within minutes of stopping her exercise. Three years ago, she developed diarrhea that was followed a week later by paresthesias in her feet and legs with a stocking distribution to the knees. Her symptoms were associated with a transient feeling of overwhelming fatigue, limiting her ambulation to 1 city block. She did not, however, have any functional weakness. After 2 weeks, milder hand and left face paresthesias developed. Four weeks later, her symptoms plateaued and persisted. Three months later, she developed more intense paresthesias and a sensation of “crawling” below both knees. At that time, she was seen at another hospital, where the examination showed bilateral pes cavus and hammertoes. There was no nerve thickening. Cranial nerves were intact. Strength was normal except for mild bilateral thenar weakness and slight difficulty with heel walking. The deep tendon reflexes were decreased at the arms and ankles. There was decreased pinprick sensation in the feet in a stocking-glove distribution with hyperalgesia. Vibration was moderately diminished at the ankles. Nerve conduction studies and electromyography (NCS/EMG) at that time showed uniform, mild conduction velocity slowing of both sensory and motor conduction with borderline prolonged distal latencies in the median and ulnar nerves. She was treated with a 1-month taper of prednisone beginning with 80 mg daily. The crawling sensation resolved and the paresthesias became less intense and stabilized. She was able to resume distance running, but still had persistent, mild numbness in her feet with bouts of increasing intensity every several months. Three years later, the patient presented to us for a …