Neurology of Nutritional Vitamin B12 Deficiency in Infants: Case Series From India and Literature Review.

We studied 27 infants aged 6 to 27 months with vitamin B12 deficiency also known as "infantile tremor syndrome" in India. All were exclusively breast-fed by vegetarian mothers. Developmental delay or regression, pallor, skin hyperpigmentation, and sparse brown hair were present in all. Majority were hypotonic and involuntary movements were encountered in 18. Anemia and macrocytosis was found in 83% and 71% infants, respectively. Low serum vitamin B12 was present in 12 of 21 infants. Seven of the 9 infants with normal serum vitamin B12 had received vitamin B12 before referral. Twelve mothers had low serum vitamin B12. Cerebral atrophy was present in all the 9 infants who underwent neuroimaging. Treatment with vitamin B12 resulted in dramatic improvement in general activity and appetite within 48 to 72 hours followed by return of lost milestones. Tremors resolved in all by 3 to 4 weeks. Nutritional vitamin B12 deficiency is a treatable cause of neurologic dysfunction in infants.