Involuntary movements may be a symptom in most infants who present with neu
rologic syndrome of infantile cobalamin (vitamin B-12) 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 characte
rized by severe involuntary movements, which were a combination of tremor a
nd myoclonus particularly involving tongue, face, pharynx, and legs. The ne
urologic symptoms improved within a few days after the administration of cl
onazepam. In each patient the mother was also cobalamin deficient and the i
nfant was solely breast-fed. The cause of involuntary movements that can ap
pear rarely after treatment in infantile cobalamin deficiency is not known.
Besides initial neurologic presenting symptoms of cobalamin deficiency, th
e occurrence of involuntary movements after treatment should also receive a
ttention. This movement disorder may disappear spontaneously, or an additio
nal treatment may be an alternative approach if the symptoms are severe. (C
) 2001 by Elsevier Science Inc. All rights reserved.