Background. Serious hematological, metabolic and neurological complications owing to the nutritional deficiency of vitamin B 12 may occur in infants of mothers on a strict vegetarian diet. Methods and Results. The mother of the first child was a strict vegetarian. She had an elevated urinary methylmalonic acid level and a low concentration of serum vitamin B 12 . Her 13-month-old daughter was exclusively breast-fed until the age of 9 month and then she was fed only vegetables. Physical examination revealed psychomotoric retardation, apathy, muscular hypotonia, abnormal movements and failure to thrive. Laboratory analysis showed a megaloblastic anaemia, a low level of vitamin B 12 and methylmalonic aciduria. MRI of the brain revealed diffuse frontotemporoparietal atrophy and retardation of meylination. After treatment with vitamin B 12 supplements, abnormal movements disappeared and development improved, but a mild generalised hypotonia continued. A cranial MRI 9 months after treatment still showed signs of retardation of myelination. The second patient, an 8 month-old male, son of a strict vegetarian mother too, was referred for investigation of psychomotoric retardation, hypotonia, dyskinesia, failure to thrive and microcephaly. He was breast-fed and from 6 month of age he had also received fruit juices. Laboratory analysis revealed megaloblastic anaemia, high methylmalonic aciduria and homocystinuria. The patient’s and his mother’s serum level of vitamin B 12 were low. After treatment with vitamin B 12 supplements, biochemical and metabolic markers of disease were normal but there continued a generalised hypotonia, microcep- haly and language delay. Conclusion. Our observations emphasize the health complications of nutritional cobalamine deficiency and a requirement of clinical, biochemical and metabolic monitoring in infants within strict vegetarian families.

        Key words: vegetarian diet, vitamin B 12 , methylmalonic aciduria, homocystinuria, microcephaly, psychomotoric retardation.