Biotinidase deficiency is an inherited disorder caused by a deficiency of the enzyme biotinidase. This enzyme is responsible for recycling biotin, a vitamin that is essential for normal growth and development. Without enough biotin, the body cannot properly use fats, carbohydrates, and proteins. Symptoms of biotinidase deficiency can include skin rash, hair loss, seizures, developmental delays, and vision problems. Treatment typically involves taking biotin supplements and avoiding foods that contain biotinase, an enzyme that breaks down biotin.