Dataset Information

Molecular genetics of phenylketonuria and tetrahydrobiopterin deficiency in Jordan.

ABSTRACT: 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.

SUBMITTER: Carducci C

PROVIDER: S-EPMC7463056 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Molecular genetics of phenylketonuria and tetrahydrobiopterin deficiency in Jordan.

Carducci Carla C Amayreh Wajdi W Ababneh Haneen H Mahasneh Amjad A Al Rababah Buthaina B Al Qaqa Kefah K Al Aqeel Momen M Artiola Cristiana C Tolve Manuela M D'Amici Sirio S Shen Nan N Yu Yongguo Y Hillert Alicia A Himmelreich Nastassja N Okun Jürgen G JG Hoffmann Georg F GF Blau Nenad N

JIMD reports 20200519 1

<h4>Background</h4>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.<h4>Objective</h4>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.<h4>Methods</h4>A total of ...[more]

PMID: 32905092

Similar Datasets

Project description:Background and purposeSevere and progressive neurologic disease remains a problem for patients with hyperphenylalaninemia due to a deficiency of tetrahydrobiopterin (BH4), even with early diagnosis and despite treatment with BH4 and neurotransmitter precursors. Few reports have included the associated imaging characteristics. Our purpose was to describe the imaging features of BH4-deficient patients identified by neonatal screening in a Taiwanese population and to correlate the imaging features with the treatment.MethodsThis study analyzed the cases of eight BH4-deficient patients who were examined by MR imaging and MR spectroscopy. Analysis of the findings was correlated with the clinical findings.ResultsOne patient whose intelligence quotient score was lower than those of the other seven patients experienced seizures in conjunction with central white matter signal changes on MR images and a lactate peak on MR spectroscopy. Lactate peak was revealed in another patient who had marked elevations of N-acetylaspartate:creatine and N-acetylaspartate:choline ratios. Although most patients had a higher than average N-acetylaspartate:creatine or N-acetylaspartate:choline ratio, the patient who had decreases of both ratios possessed the highest intelligence quotient scores among the eight patients. In addition, the myoinositol:choline ratio correlated positively with the average BH4 dosage (P =.027, r = 0.027) and the choline:creatine ratio correlated negatively with the average 5-hydroxytryptophan dosage (P =.035, r = -0.742).ConclusionCompared with classical phenylketonuria, patients with BH4 deficiency have fewer white matter changes revealed by MR imaging but more changes revealed by MR spectroscopy. MR spectroscopy is a potential method with which to monitor the dosages of supplements used to treat this disorder. In addition, MR spectroscopy may be helpful in gaining understanding of the neurophysiological changes that occur in association with this disease.

Project description:A need exists to expand the characterization of tetrahydrobiopterin (BH(4)) responsiveness in patients with phenylketonuria (PKU), beyond simply evaluating change in blood phenylalanine concentrations. The clinical interpretation of BH(4) responsiveness should be evaluated within the context of phenylalanine hydroxylase (PAH) genotype.This investigation seeks to use a modified version of a previously developed PAH genotype severity tool, the assigned value (AV) sum, to assess the molecular basis of responsiveness in a clinical cohort and to explore the tool's ability to differentiate BH(4) responsive groups.BH(4) response was previously clinically classified in 58 patients with PKU, with three response groups emerging: definitive responders, provisional responders, and non-responders. Provisional responders represented a clinically ambiguous group, with an initial decrease in plasma phenylalanine concentrations, but limited ability to improve dietary phenylalanine tolerance. In this retrospective analysis, mutations in the PAH gene were identified in each patient. PAH genotype was characterized through the AV sum approach, in which each mutation is given an AV of 1, 2, 4, or 8; the sum of both mutations' AV corresponds to genotype severity, with a lower number representing a more severe phenotype. An AV sum cutoff of 2 (indicative of the most severe genotypes) was used to dichotomize patients and predict BH(4) responsiveness. Provisional responders were classified with the definitive responders then the non-responders to see with which group they best aligned.In 17/19 definitive responders, at least one mutation was mild or moderate in severity (AV sum>2). In contrast, 7/9 provisional responders carried two severe or null mutations (AV sum=2), suggesting little molecular basis for responsiveness. Non-responders represent a heterogeneous group with 15/25 patients carrying two severe mutations (AV sum=2), 5/25 patients carrying one moderate or mild mutation in combination with a severe or null mutation (AV sum>2), and the remaining five patients carrying an uncharacterized mutation in combination with a severe mutation. Predictive sensitivity of the AV sum was maximized (89.5% vs. 67.9%) with limited detriment to specificity (79.4% vs. 80.0%), by classifying provisional responders with the non-responders rather than with the definitive responders.In our clinical cohort, the AV sum tool was able to identify definitive responders with a high degree of sensitivity. As demonstrated by both the provisional responder group and the substantial number of non-responders with AV sums>2, a potential exists for misclassification when BH(4) response is determined by relying solely on change in plasma phenylalanine concentrations. PAH genotype should be incorporated in the clinical evaluation of BH(4) responsiveness.

Dataset Information

Molecular genetics of phenylketonuria and tetrahydrobiopterin deficiency in Jordan.

Publications

Molecular genetics of phenylketonuria and tetrahydrobiopterin deficiency in Jordan.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets