Maternal vegan diet causing a serious infantile neurological disorder due to vitamin B12 deficiency

We present a 9-month-old exclusively breastfed baby of a strict vegetarian mother who had excluded all animal proteins from her diet. The patient's symptoms included dystrophy, weakness, muscular atrophy, loss of tendon reflexes, psychomotor regression and haematological abnormalities. Biochemical investigations revealed severe methylmalonic aciduria and homocystinuria in the patient, slight methylmalonic aciduria in the mother and low concentrations of serum vitamin B₁₂ in both patient and mother.Presented in preliminary form at the Annual Meeting of the Swiss Paediatric Society, Geneva, 12–13 June 1987