What Your Test Results Mean:

Carriers typically do not show any signs or symptoms of biotinidase deficiency; however, carriers are at an increased risk of having a child with biotinidase deficiency for current or future pregnancies, depending on your partner’s carrier status. Carrier testing of your partner is recommended, in addition to consulting with a genetic counselor.

Disease Explained:

Biotinidase deficiency is an inherited metabolic disorder that can present with seizures, hypotonia (weak muscle tone), and breathing issues in the newborn period. The BTD gene makes the enzyme biotinidase that aids the body in reusing biotin, a B vitamin that is essential for breaking down fats, proteins, and carbohydrates. Individuals with biotinidase deficiency have decreased or eliminated activity of biotinidase. Without enough of this enzyme, biotin cannot be recycled normally within the body. If not properly treated, developmental delay, vision loss and hearing loss, ataxia (issues with movement and balance), skin rashes, and alopecia (hair loss) may develop. Treatment involves lifelong management with biotin supplements, which can lessen and prevent many of the complications from biotinidase deficiency.

How the Genetics Works:

Biotinidase deficiency is an autosomal recessive disorder caused by pathogenic variants in the BTD gene. All individuals have two copies of the BTD gene. Carriers of biotinidase deficiency have a variant in one copy of the BTD gene while individuals with biotinidase deficiency have variants in both copies of BTD, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.