Background: Serious hematological, metabolic and neurological complications owing to the nutritional deficiency of vitamin B12 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 B12. 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 B12 and methylmalonic aciduria. MRI of the brain revealed diffuse frontotemporoparietal atrophy and retardation of myelination. After treatment with vitamin B12 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 B12 were low. After treatment with vitamin B12 supplements, biochemical and metabolic markers of disease were normal but there continued a generalised hypotonia, microcephaly 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.