• Ozlem Oz, Meryem Karaca, Nurgul Atas, Ataman Gonel, and Mujgan Ercan.
• Department of Medical Genetics, Faculty of Medicine, Harran University Sanliurfa, Turkey.
• J Coll Physicians Surg Pak. 2021 Jul 1; 31 (7): 780785780-785.

ObjectiveTo identify the biotinidase (BTD) gene mutations in patients with biotinidase deficiency in our region; and to determine the phenotype-genotype correlations in the presence of clinical findings.Study DesignDescriptive study.Place And Duration Of StudyDepartment of Medical Genetics and Pediatric Metabolism Outpatient Clinic, Faculty of Medicine, Harran University, between January 2018 and June 2020.MethodologyTwo hundred and nine patients, who were found positive for biotinidase deficiency in heel blood screening, were included. Genomic DNA was isolated from peripheral blood. Next-generation DNA sequencing analysis was performed using primers covering the exon regions of the BTD gene. The results were analysed by the mutation surveyor programme.ResultsThe most common mutation was c.1330 G>C (p.D444H) and the second most common mutation was c.470 G>A (p.R157H). The majority of the mutations are missense; and they are especially located in the exon 4. The most frequent mutations were found to be D444H and R157H with a rate of 66.66% in symptomatic patients.ConclusionCommon mutations in BTD deficiencies were indentified. Associating them with phenotype-genotype data will assist clinicians in better genetic counselling and management in the future by implementing prevention programmes. Key Words: Biotinidase deficiency, BTD gene, Newborn screening, Inherited metabolic disease, Newborn screening programme.

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