Cobalamin E defect, a rare inborn error of vitamin B12 metabolism: value of early diagnosis and treatment.

Cobalamin and its metabolites play a crucial role in DNA synthesis and cellular energy metabolism. Disorders of cobalamin metabolism are rare, autosomal recessive, conditions that present with neurological dysfunction of varying severity. We report a child with cobalamin E defect presenting in early infancy with vertical nystagmus, developmental delay, deceleration in head growth, status epilepticus and leukoencephalopathy, with only mild haematological abnormalities. Resolution of seizures and subsequent improvement in development and head growth was observed following early treatment with parenteral hydroxocobalamin, betaine, folate and methionine, emphasising the importance of early diagnosis and treatment in these conditions.