Prolonged exclusive breast-feeding from vegan mother causing an acute onset of isolated methylmalonic aciduria due to a mild mutase deficiency.

[homocystinuria without methylmalonic aciduria]

We describe a case of methylmalonic aciduria (MMA ) occurred in a 22 -month -old boy whose diet was exclusively based upon breast -feeding from a mother following a long -lasting strict vegetarian diet . Clinical picture showed a dramatic onset , with a profound drowsiness associated with a severe metabolic acidosis , hyperammonemia , macrocytic anemia , ketonuria , and massive methylmalonic aciduria without homocystinuria . Both symptoms and biochemical findings quickly improved thanks to prompt vitamin B (12 )parenteral therapy . Biochemical and enzymatic findings allowed a diagnosis of mild mutase deficiency , which only and inadequate dietary B (12 )contribution might have revealed . Our case highlights the risk of a prolonged strictly vegetarian diet of lactating mother for providing inadequate amounts of some nutrients to the breast -fed baby . Moreover , such a dietary behaviour could dramatically unmask otherwise clinically unapparent metabolic defects in the baby .