Say N2O to Drugs: A Unique Presentation of Symptomatic Vitamin B12 Deficiency

A 19-year-old woman with no past medical history presented with 1 month of progressive bilateral hand and feet numbness and ataxic gait. Her history was unremarkable. She denied visual changes, fever, chills, night sweats, cough, nausea, vomiting, or diarrhea. She had no history of surgeries, consumed a normal diet, and denied substance abuse. Her vital signs were normal, and her physical examination was unremarkable except for the neurologic examination. This revealed diminished sensation to light touch, pinprick, and vibratory sense in a stocking glove distribution affecting dermatomes C5-T1 and L5-S3, brisk 3+ patellar reflexes, a broad-based gait requiring a walker, and a positive Romberg test.