Involuntary movements in infantile cobalamin deficiency appearing after treatment.

Involuntary movements may be a symptom in most infants who present with neurologic syndrome of infantile cobalamin (vitamin B12) deficiency. In this report, two infants with cobalamin deficiency are presented. These patients also developed a striking movement disorder that appeared a few days after treatment with intramuscular cobalamin. The movement disorder was characterized by severe involuntary movements, which were a combination of tremor and myoclonus particularly involving tongue, face, pharynx, and legs. The neurologic symptoms improved within a few days after the administration of clonazepam. In each patient the mother was also cobalamin deficient and the infant was solely breast-fed. The cause of involuntary movements that can appear rarely after treatment in infantile cobalamin deficiency is not known. Besides initial neurologic presenting symptoms of cobalamin deficiency, the occurrence of involuntary movements after treatment should also receive attention. This movement disorder may disappear spontaneously, or an additional treatment may be an alternative approach if the symptoms are severe.