Description - This metabolic disorder is an autosomal recessive disorder. Biotinidase is an enzyme that is required to produce free biotin from dietary, intestinal bacterial, or recycled sources of its precursor, biocytin. This disorder is a form of multiple carboxylase deficiency that usually presents in the neonatal period (median age 3 months).
Clinical Features - Infants with biotinidase deficiency appear to be normal at birth, but if not treated develop one or more of the following signs after the first weeks or months of life: hypotonia, ataxia, seizures, developmental delay, hair loss, seborrhea, dermatitis, hearing loss, and optic nerve atrophy. Some affected children may have episodes of life-threatening metabolic acidosis.
Treatment – Early diagnosis and treatment with daily prescribed biotin supplements prevents signs and symptoms. Presymptomatic treatment generally results in completely normal development, including normal vision and hearing. In children diagnosed outside of the newborn period (not identified by newborn screening), daily prescribed biotin supplements will clear the skin rash and hair loss and improve the neurological status. With the exception of auditory and optic nerve losses, the majority of clinical manifestations can be reversed in patients with a delay in diagnosis.