[Maternal Crohn's disease-related vitamin B12 deficient megaloblastic anemia in an infant].

We report an 11-month-old breast-fed boy with feeding difficulties, lethargy, and developmental delay. Blood examination showed pancytopenia and decreased serum levels of vitamin B12. Anisocytosis and poikilocytes were detected in his peripheral blood, and increased megaloblastosis without leukemic cells was detected in his bone marrow. After the diagnosis of megaloblastic anemia due to vitamin B12 deficiency, symptoms were improved by vitamin B12 administration. Further investigation of the mother identified Crohn's disease and suggested that the supply of vitamin B12 from the mother to the infant, via the placenta during pregnancy and via breast milk after birth, was decreased due to impaired absorption of vitamin B12 in the mother's small intestine. Magnetic resonance imaging of the boy's brain on admission showed cerebral cortex atrophy which had improved by the age of 1 year and 10 months after vitamin B12 treatment, though developmental delay was still evident at the age of 3 years. Infantile vitamin B12 deficiency often presents with nonspecific manifestations, such as developmental delay and failure to thrive, in addition to anemia and is thus not easily diagnosed. To prevent severe neurological sequelae, this condition must be rapidly diagnosed, because a prolonged duration increases the risk of permanent disabilities.