12/29/2025
Biotinidase deficiency is a rare inherited metabolic disorder caused by mutations in the BTD gene, leading to insufficient activity of the enzyme biotinidase. This enzyme is essential for recycling biotin, a vitamin critical for carboxylase enzyme function involved in fatty acid synthesis, amino acid catabolism, and gluconeogenesis. Without adequate biotinidase activity, affected individuals develop neurological, dermatological, and immunological symptoms, including seizures, hypotonia, developmental delay, eczema, hair loss, and recurrent infections. The condition is autosomal recessive, meaning both copies of the gene must be mutated for symptoms to appear. Early newborn screening allows prompt treatment with oral biotin supplementation, which can prevent severe complications and improve long-term outcomes. Untreated, the disorder may lead to irreversible neurological damage.
