Biotinidase Deficiency (BTD)
Biotinidase deficiency is an autosomal recessive disorder caused by pathogenic variants in the gene BTD. This pan-ethnic disorder affects individuals within the first few months of life. Severe forms of the disorder cause children to experience neurological abnormalities such as seizures, hypotonia, developmental delay, and vision problems as well as hearing problems, respiratory problems, and cutaneous abnormalities. While effective treatment is available, symptoms such as vision problems, hearing loss, and developmental delay are irreversible. Several specific variants have been associated with full or partial biotinidase deficiency, and therefore the severity of the disease may be predicted based on the genotype.
For information about carrier frequency and residual risk, please see the residual risk table.