Holocarboxylase synthetase deficiency: 9-year follow-up of a patient on chronic biotin therapy and a review of the literature.

We report on the long-term medical and neurodevelopmental follow-up of a patient with the rare and potentially lethal disease, holocarboxylase synthetase deficiency. He was originally treated prenatally with biotin megatherapy and for 9 years with 6 mg/day since his only episode of fulminant acidosis at 3 months of age. While growth and general health have been normal, the patient has exhibited signs of minimal brain dysfunction. However, evaluation of unaffected siblings suggests that this may be unrelated to his metabolic disease. A review of the literature and recommendations for optimal treatment are provided.