Background: Biotin, a water-soluble vitamin, is used as a co-factor by enzymes involved in carboxylation reactions. It functions as the carboxyl carrier for biotin-dependent carboxylases. These enzymes catalyze gluconeogenesis, fatty acid metabolism and amino acid catabolism, thus biotin plays an essential role in maintaining metabolic homeostasis. Biotinidase deficiency is an inherited metabolic disorder characterized by neurological and cutaneous symptoms, treated by oral administration of the vitamin biotin. In central Anatolia marriages between relatives are very common (26%).