Thesis (Ph.D.) - Cairo University - Faculty of Medicine - Department of Pediatrics

If untreated, children with biotinidase deficiency usually exhibit seizures, hypotonia, ataxia, global developmental delay, vision problems, hearing loss and cutaneous abnormalities (alopecia, skin rash, and candidiasis). The deficiency of the enzyme may be profound ({u02C2}10%) or partial (10-30%), all symptomatic children improve when treated with 5-10mg of oral biotin/day while those identified by newborn screening should remain asymptomatic if the treatment is instituted early and continuously lifelong. In this study, the frequency, clinical profile and molecular infrastructure of biotinidase deficiency among high risk children were depicted. Methods: Serum biotinidase is determined by colorimetric technique followed by sequencing of BTD gene in deficient patients. Results: Being an autosomal recessive neurocutaneous disease, biotinidase deficiency is frequent (11%) among our studied group owing to high degree of consanguinity; the more severe phenotype due to profound deficiency is more common than the less severe partial one. Most of our studied patients (88.8%) exhibited homozygous private novel mutations in exon 4. Conclusion: High index of suspicion should be maintained to identify patients with biotinidase deficiency early to institute biotin therapy and prevent disabling neurological sequalae, till a nationwide newborn screening program is implemented

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