An infant and mother with severe B₁₂ deficiency: vitamin B₁₂ status assessment should be determined in pregnant women with anaemia

Abstract

The vitamin B₁₂ status of infants depends on maternal B₁₂ status during pregnancy, and during lactation if breastfed. We present a 9-month-old girl who was admitted to the metabolic unit for assessment of developmental delay. She was exclusively breastfed and the introduction of solids at 5 months was unsuccessful. Investigations revealed pancytopenia, undetectable B₁₂ and highly elevated methylmalonic acid and homocysteine. Methylmalonic acid and homocysteine normalised following B₁₂ injections. Marked catch-up of developmental milestones was noted after treatment with B₁₂. Investigations of parents showed normal B₁₂ in the father and combined B₁₂ and iron deficiency in the mother. Maternal B₁₂ deficiency, most likely masked by iron deficiency, led to severe B₁₂ deficiency in the infant. Exclusive breastfeeding and a subsequent failure to wean exacerbated the infant’s B₁₂ deficiency leading to developmental delay. This case highlights the need for development of guidelines for better assessment of B₁₂ status during pregnancy.