Vitamin B₁₂ deficiency in a breast fed infant

We report the case of a 5 month old breast fed infant who presented with a history of vomiting, pallor, and failure to thrive. Investigations showed severe nutritional vitamin B₁₂ deficiency with a megaloblastic pancytopenia. This deficiency was due to low vitamin B₁₂ concentrations in the maternal breast milk, and subsequent investigations showed maternal pernicious anaemia. Treatment of the infant with vitamin B ₁₂ resulted in a rapid clinical and haematological improvement. This case represents an unusual presentation of pernicious anaemia.