Background: Biotinidase-Deficiency is an autosomal recessive disorder with a wide range of symptoms: Asymptomatic forms and severe neurological symptoms have been described so far. Only very few cases are described with visual impairment and hearing loss, however it seems very unclear whether these symptoms are specific for the disease or rather due to treatment (Wolf, 1983).

Subjects: In 12 children affected with this disorder (6 m, 6 f, age 3-21 years) without any symptoms visual evoked potentials have been measured by using checkerbord pattern stimuli; criteria for judgment of VEP's were: prolongation of latency of component P2 (M+2, 5 SD) and/or severe deformation of this component.

Results: In at least 9/12 affected children abnormal evoked visual potentials have been found; the latency of P2 was prolonged in 9 subjects, a deformation of the component was found in 5 subjects. 2 of all children had completely normal VEP's. There was no relationship between the abnormality of VEP and the rest-activity of biotinidase.

Discussion: Until now no data are available in regards to electrophysiological abnormalities in subjects with BD, however there are reports on patients with diminished eyesight. Therefore it seems very important to know parameters, which might indicate that the entire patient is at risk for eye abnormalities and therefore he should be treated prophylactically. Longterm follow-up of those patients should be performed in order to find out whether these abnormalities are preliminary stages of later visual impairment.

It is speculated that impaired VEP's in asymptomatic patients with BD could indicate a need for early treatment with biotin.