Objective Biotin, a water-soluble vitamin, is used as a co-factor for enzymes involved in carboxylation reactions. It functions as the carboxyl carrier for biotin-dependent carboxylases. These enzymes catalyse 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 characterised by neurological and cutaneous symptoms, prevented by oral administration of the vitamin biotin. In central Anatolia marriages between relatives are very common (26%).

Methods We screened 34 378 infants born in four cities in central Anatolia during the one-year period beginning February 2006 for deficiency of the enzyme biotinidase. A simple colorimetric screening procedure was used to detect the presence or absence of biotinidase activity on the same blood-soaked filter paper cards. Positive samples were confirmed with the quantitative method.

Results One newborn infant with partial biotinidase deficiency (10–30% of mean normal serum activity) was identified during the 12-month pilot study. The estimated incidence of partial biotinidase deficiency in central Anatolia is approximately 1 : 34 378, this ratio was the same in findings from Istanbul (1 : 33 307).

Conclusions Like children with profound biotinidase deficiency, children with partial biotinidase deficiency are symptom-free at birth. However, the subsequent occurence of symptoms of profound biotinidase deficiency in our patient with partial deficiency suggests that biotin therapy for this condition may be warranted. It is known that in Turkey marriages between relatives are common. If the neonatal screening programme is widened the real ratio can be determined, where marriages between relatives are very high in central Anatolia.