Congenital B12 deficiency following maternal gastric bypass.

Here we present a case of severe B12 deficiency in an exclusively breastfed infant, born to a mother who had undergone gastric bypass 6 years earlier. At 4 months of age, the infant presented with pancytopenia and developmental delay. Our evaluation revealed physical and neurological developmental delay, pancytopenia with macrocytosis, with head imaging showing cortical and subcortical atrophy. Serum studies showed low B12, normal folate and iron. Treatment with parenteral B12 led to the resolution of the pancytopenia, steady weight gain and improved neurological status. The child is currently 16 months old with normal anthropometric and hematological parameters and normal B12 levels on a regular diet. Gross motor and speech developments are significantly delayed. This case illustrates that maternal B12 deficiency following gastric bypass surgery may lead to severe B12 deficiency with long-term neurological sequelae in their infants. Screening and prompt treatment of these deficiencies both during pregnancy and during infancy are important.