Multiple carboxylase deficiency (late onset) due to deficiency of biotinidase.

Biotinidase is a ubiquitous mammalian cell enzyme occurring in liver, serum and kidney. It cleaves biotin from biocytin, which is a cofactor for biotin dependent enzymes, namely the human carboxylases. Biotinidase deficiency is associated with a wide spectrum of neurological, dermatological, immunological and ophthalmological abnormalities. This is a case of a 3-year-old boy presenting with delayed developmental milestones, tachypnea, progressively increasing ataxia, alopecia and dermatitis, all which dramatically responded to high doses of biotin.