Biotinidase is an enzyme that recycles biotin, a water-soluble vitamin essential as a coenzyme for four carboxylases that are involved in gluconeogenesis, fatty acid synthesis, and in the catabolism of several branch-chain amino acids. Biotinidase deficiency (BD) is an autosomal recessively inherited disorder. Patients with profound BD (<10% of mean normal serum biotinidase activity) presents, usually during early childhood, with neurological (seizures, hypotonia, ataxia, developmental delay, vision problems, and/or hearing loss) and non-neurological findings (metabolic acidosis, respiratory difficulties, alopecia and/or skin rash) that may progress to coma or death if untreated.