Identification and Characterization of BTD Gene Mutations in Jordanian Children with Biotinidase Deficiency

Biotinidase deficiency is an autosomal recessive metabolic disorder whose diagnosis currently depends on clinical symptoms and a biotinidase enzyme assay. This study aimed to investigate the mutational status and enzymatic activity of biotinidase deficiency in seven unrelated Jordanian families including 10 patients and 17 healthy family members. Amplified DNA was analyzed by the automated Sanger sequencing method, and the enzymatic assay was performed using a colorimetric assessment. Biotinidase level was significantly lower (p < 0.001) in BTD children compare to their non-affected family members. Genetic sequencing revealed six different mutations in Jordanian patients. One mutation was novel and located in exon 4, which could be a prevalent mutation for biotinidase deficiency in the Jordanian population. Identification of these common mutations and combing the enzymatic activity with genotypic data will help clinicians with regard to better genetic counseling and management through implementing prevention programs in the future

Molecular genetics of phenylketonuria and tetrahydrobiopterin deficiency in Jordan

Background Information regarding the prevalence of PKU in the Middle East in comparison to other world regions is scarce, which might be explained by difficulties in the implementation of national newborn screening programs. Objective This study seeks for the first time to genotype and biochemically characterize patients diagnosed with hyperphenylalaninemia (HPA) at the Pediatric Metabolic Genetics Clinic at the King Hussein Medical Center, Amman, Jordan. Methods A total of 33 patients with HPA and 55 family members were investigated for pterins (neopterin and biopterin) and dihydropteridine reductase (DHPR) activity in dried blood spots. Patients with HPA were genotyped for phenylketonuria (PKU) and the genes involved in tetrahydrobiopterin (BH$_{4}$) metabolism. Results In total 20 patients were diagnosed with PKU due to phenylalanine hydroxylase (PAH) deficiency, 2 with GTP cyclohydrolase I (GTPCH) deficiency, 6 with DHPR deficiency, and 3 with the 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency. Diagnosis was not possible in 2 patients. This study documents a high percentage of BH$_{4}$ deficiencies within HPA patients. With one exception, all patients were homozygous for particular gene variants. Conclusions This approach enables differentiation between PKU and BH$_{4}$ deficiencies and, thus, allows for critical selection of a specific treatment strategies

Molecular genetics of phenylketonuria and tetrahydrobiopterin deficiency in Jordan

Background: Information regarding the prevalence of PKU in the Middle East in comparison to other world regions is scarce, which might be explained by difficulties in the implementation of national newborn screening programs. Objective: This study seeks for the first time to genotype and biochemically characterize patients diagnosed with hyperphenylalaninemia (HPA) at the Pediatric Metabolic Genetics Clinic at the King Hussein Medical Center, Amman, Jordan. Methods: A total of 33 patients with HPA and 55 family members were investigated for pterins (neopterin and biopterin) and dihydropteridine reductase (DHPR) activity in dried blood spots. Patients with HPA were genotyped for phenylketonuria (PKU) and the genes involved in tetrahydrobiopterin (BH4) metabolism. Results: In total 20 patients were diagnosed with PKU due to phenylalanine hydroxylase (PAH) deficiency, 2 with GTP cyclohydrolase I (GTPCH) deficiency, 6 with DHPR deficiency, and 3 with the 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency. Diagnosis was not possible in 2 patients. This study documents a high percentage of BH4 deficiencies within HPA patients. With one exception, all patients were homozygous for particular gene variants. Conclusions: This approach enables differentiation between PKU and BH4 deficiencies and, thus, allows for critical selection of a specific treatment strategies