Clinical and neuropsychological outcome in 33 patients with biotinidase deficiency ascertained by nationwide newborn screening and family studies in Austria

Newborn screening for biotinidase deficiency (BD) provides prevention of neurological sequelae in patients with low residual enzyme activity by early treatment with oral biotin substitution. Screening 1.1 million newborns in Austria and consecutive family studies led to the identifcation of 21 patients with profound BD (residual activity 1%–<10% (n=16) respectively. Evaluation of clinical and neuropsychological outcome showed that only patients with a biotinidase activity <1% (n=3/5) exhibited characteristic clinical symptoms within the first weeks of life, while five patients with a residual activity of 1.2%–4.6% did not develop clinical symptoms even when not treated until 3.5–21 years. In all patients with residual activity <10% and biotin substitution within the first weeks of life, neuropsychological outcome was normal, while abnormal in three out of five patients tested for IQ and treated after the age of 3.5 years. In five out of nine patients with poor compliance or delayed or no treatment, visual and brainstem auditory evoked potentials were measured and were within age-related normal values. All patients with partial BD available for follow-up remained clinically and neuropsychologically asymptomatic without treatment at ages 2.5–10 years.