RESUMO
BACKGROUND: Vitamin B 12 deficiency is an uncommon disorder in infancy. Most cases are because of maternal deficiency resulting from insufficient storage and/or reduced intake and are generally seen in exclusively breast-fed infants. Accentuation of the hemolytic process has never been described in association with Varicella Zoster Virus (VZV) infections. OBSERVATION: We describe a 9-months-old breast-fed infant with megaloblastic anemia secondary to maternal vitamin B 12 deficiency. He presented severe pancytopenia and regression of motor functions and developed hemolytic crisis during a VZV infection. CONCLUSIONS: Nutritional cobalamin deficiency should be considered in anemic infants with a history of prolonged exclusive breastfeeding and delayed developmental milestones. VZV infection can trigger a hemolytic process in infants with severe megaloblastic anemia secondary to B12 deficiency. A normal mean corpuscular volume does not rule out megaloblastic anemia, when the condition is combined with severe hemolysis.
