International Journal of Pediatric Otorhinolaryngology
Audiologic findings in children with biotinidase deficiency in Turkey
Introduction
Biotinidase deficiency (BD) is an autosomal recessively inherited disorder that results in failure to recycle the vitamin, biotin [1]. The clinical features of biotinidase deficiency include seizures, hypotonia, ataxia, respiratory problems, skin rash, alopecia, hearing loss, optic atrophy, conjunctivitis, fungal infections and developmental delay [2], [3], [4]. The disorder can be effectively treated with pharmacologic doses of biotin [1]. Following biotin treatment, neurologic symptoms typically resolve in hours to days and the cutaneous manifestations disappear in a few weeks [1], [5].
Sensorineural hearing loss has been reported in 20–76% of symptomatic children with BD [1], [6]. Although the degree of hearing loss is reported to be variable, it is typically moderate to severe-profound loss with upward or downward sloping character [1]. Hearing loss appears to be irreversible with treatment, however, in at least one child it was reversible [2].
In the present study, we have characterized the hearing status of a Turkish population of children with BD ascertained because they presented with symptoms or because they had an older sibling with the disorder.
Section snippets
Subjects
Children with BD were ascertained by the Pediatric Nutrition and Metabolism Unit in Hacettepe University Faculty of Medicine between the years 1996 and 2005. A total of 20 children with profound BD, half male and half female, were evaluated in the Audiology Unit (Table 1). The study was approved by the Ethical Committee of the university (No. HEK 05/94-5).
Biotinidase activity
Serum biotinidase activities were determined using a colorimetric assay that measures the release of p-aminobenozate from the substrate
Results
Clinical characteristics and serum biotinidase activities of the children are summarized in Table 1. With the exception of one child, all individuals with BD were the product of first-degree consanguineous marriages. Sixteen children were diagnosed because they exhibited clinical and laboratory signs and symptoms, such as seizures, dermatitis, alopecia, and lactic acidosis. The mean age of diagnosis was 18.8 months (range: 0.1–30 months). All these children were on biotin treatment at the time
Discussion
BD is an inherited metabolic disorder of biotin recycling [1]. BD is common in Turkey because of the high frequency of consanguinity [9], [12]. All parental couples but one in our study were known to be of first-degree consanguineous matings. BD is not included in newborn screening in Turkey, with the exception of one local center. Therefore, it is difficult to diagnose affected individuals in Turkey before the onset of symptoms [13].
Untreated children with profound BD may develop
Acknowledgments
The authors thank to chemical engineer Hatice Onat for enzyme measurements, to Erdem Karabulut, PhD for statistical analysis and to all patients and parents for their collaboration to this study. Portions of this work were funded by the Safra Research Fund to B.W.
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