Vitamin B12 Enzyme Deficiency Causing Mental Status Changes and Abnormal Gait

A 13-year-old boy developed an unsteady gait after changing to a vegetarian diet for 15 days. He had impairments in temporal and spatial orientation, calculation, and short-term memory on mental status examination and horizontal nystagmus, spastic gait, and bilateral ankle clonus and Babinski signs on physical examination (Video). Increased homocysteine levels (8.85 mg/L; reference, less than 2.03 mg/L [to convert to micromoles per liter, multiply by 7.397]) and methylmalonic acidemia on urine organic acid analysis confirmed a deficiency of cobalamin C (CblC), an enzyme that converts dietary vitamin B12 into its 2 metabolically active forms. His symptoms and gait improved with folate, methyl-cobalamin, and levocarnitine supplementation. Click https://ja.ma/3w1dVJ2 for full case details and discussion.

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