Involuntary movements associated with vitamin B12 deficiency.

Involuntary movements are not a known feature of vitamin B12 (vB12) deficiency in adults, though they are a characteristic feature of vB12 deficiency in infants. This case report presents an adult patient with vB12 deficiency in whom, myoclonus-like muscular contractions appeared soon after the initiation of vB12 and disappeared after the first week of this therapy. To our knowledge, this is the first report of involuntary movements in an adult patient with vB12 deficiency. Although the mechanism remains unknown, involuntary movements similar to myoclonus should be considered as one of the extraordinary neurological manifestations of vB12 deficiency in adults.