Limbic System and Optic Nerve Diffusion Restriction in a Child with Biotinidase Deficiency

Congenital biotinidase deficiency (CBD) is a rare, autosomal recessive, reversible metabolic encephalopathy caused by pathogenic variants in the biotinidase ( BTD ) gene (Online Mendelian Inheritance in Man 609019). Biotin serves as a cofactor for four carboxylase enzymes (pyruvate carboxylase, propionyl CoA carboxylase, 3-meth-ylcrotonyl CoA carboxylase, and acetyl CoA carboxylase) required for fatty acid synthesis, amino acid metabolism, and gluconeogenesis. A deficiency in biotinidase disrupts biotin recycling and the release of biotin bound to dietary proteins, leading to reduced biotin availability for carboxylase enzymes. This results in energy depletion and metabolic acidosis [1].