Biotinidase deficiency: the importance of adequate follow-up for an inconclusive newborn screening result

Biotinidase deficiency is an inherited metabolic disorder characterized by inability to recycle protein-bound biotin. It usually presents with ataxia and seizures, though atypical presentations have also been described. We report a 15-month-old boy with profound biotinidase deficiency who presented with laryngeal stridor and subsequently developed severe ataxia and lactic acidosis. Subsequently, it was discovered that the patients newborn screening test for biotinidase activity had been inconclusive, but confirmatory testing had not been done. Brain magnetic resonance imaging showed multiple white matter non-enhancing T2 hyperintensities, which largely resolved following 6 months of biotin therapy; however, there was residual deafness and mental retardation. Conclusion:An argument is made for universal newborn screening in biotinidase deficiency and improved mechanisms for follow-up of positive screens, because delay in diagnosis results in irreversible morbidity, newborn screening is cost effective, and early therapy prevents the neurologic sequelae.