Neonatal screening for biotinidase deficiency in east-Hungary

There are two types of multiple carboxylase deficiency, the neonatal form with holocarboxylase synthetase defect and the late-onset form with biotinidase deficiency. We report our preliminary experiences in screening for biotinidase deficiency. In total 43,493 infants were screened for the deficiency of the enzyme biotinidase; 0.14% false positive results that necessitated requests for second blood samples and two newborns with a biotinidase defect were identified during our pilot study. The definitive diagnosis required the demonstration of enzyme deficiency in serum. Both of the patients have residual biotinidase activity: 3.59% and 7.55%. These two newborns with biotinidase deficiency are treated with daily supplementation of free biotin. According to our preliminary results biotinidase deficiency satisfies all the criteria for incorporation into the national newborn mass screening.