(MCD, holocarboxylase synthetase) Multiple carboxylase deficiency
A deficiency of biotin, part of the Vitamin B complex, leading to multiple carboxylase deficiency. Incidence is 1 in 87,000. Symptoms include seizures, hypotonia, immune system impairment, skin rashes, hair loss, hearing loss and mental retardation. Treatment is oral biotin supplementation, which should be begun immediately upon diagnosis.