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Population genetics of hyperphenylalaninaemia resulting from phenylalanine hydroxylase deficiency in Portugal.

ABSTRACT: In order to elucidate the molecular basis of phenylketonuria (PKU) in Portugal, a detailed study of the Portuguese mutant phenylalanine hydroxylase (PAH) genes was performed. A total of 222 mutant alleles from 111 PKU families were analysed for 26 mutations and restriction fragment length polymorphismlvariable number tandem repeat (RFLP/VNTR) haplotypes. It was possible to characterise 55% of the mutant alleles, in which 14 different mutations (R261Q, V388M, IVS10nt-11, I65T, P281L, R252W, R158Q, L348V, Y414C, L311P, Y198fsdel22bp, R408W, R270K, and R261X) and three polymorphisms (Q232Q, V245V, and L385L) were identified. A total of 14 different haplotypes were observed, with a high prevalence of haplotype 1 among mutant and normal alleles. The results reported in this study show considerable genetic heterogeneity in the Portuguese PKU population, as has also been described for other southern European populations.

SUBMITTER: Rivera I

PROVIDER: S-EPMC1051278 | biostudies-other | 1998 Apr

REPOSITORIES: biostudies-other

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Population genetics of hyperphenylalaninaemia resulting from phenylalanine hydroxylase deficiency in Portugal.

Rivera I I Leandro P P Lichter-Konecki U U Tavares de Almeida I I Lechner M C MC

Journal of medical genetics 19980401 4

In order to elucidate the molecular basis of phenylketonuria (PKU) in Portugal, a detailed study of the Portuguese mutant phenylalanine hydroxylase (PAH) genes was performed. A total of 222 mutant alleles from 111 PKU families were analysed for 26 mutations and restriction fragment length polymorphismlvariable number tandem repeat (RFLP/VNTR) haplotypes. It was possible to characterise 55% of the mutant alleles, in which 14 different mutations (R261Q, V388M, IVS10nt-11, I65T, P281L, R252W, R158Q ...[more]

PMID: 9598724

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Project description:Phenylalanine hydroxylase (PAH) deficiency is a genetic disorder characterized by deficiency of the PAH enzyme. Patients follow a phenylalanine-restricted diet low in intact protein, and must consume synthetic medical food (MF) to supply phenylalanine-free protein. We assessed relationships between dietary intake and nutrient source (food or MF) on bone mineral density (BMD) and bone turnover markers (BTM) in PAH deficiency. Blood from 44 fasted females 11-52 years of age was analyzed for plasma phenylalanine, serum BTM [CTx (resorption), P1NP (formation)], vitamin D, and parathyroid hormone (PTH). BTM ratios were calculated to assess resorption relative to formation (CTx/P1NP). Dual energy X-ray absorptiometry measured total BMD and age-matched Z-scores. Three-day food records were analyzed for total nutrient intake, nutrients by source (food, MF), and compliance with MF prescription. Spearman's partial coefficients (adjusted for age, BMI, energy intake, blood phenylalanine) assessed correlations. All had normal BMD for age (Z-score >-2). Sixty-four percent had high resorption and normal formation indicating uncoupled bone turnover. CTx/P1NP was positively associated with food phenylalanine (r 2 = 0.39; p-value = 0.017), energy (r 2 = 0.41; p-value = 0.011) and zinc (r 2 = 0.41; p-value = 0.014). CTx/P1NP was negatively associated with MF fat (r 2 = -0.44; p-value = 0.008), MF compliance (r 2 = -0.34; p-value = 0.056), and positively with food sodium (r 2 = 0.43; p-value = 0.014). CTx/P1NP decreased significantly with age (p-value = 0.002) and higher PTH (p-value = 0.0002). Phenylalanine was not correlated with any bone indicator. Females with PAH deficiency had normal BMD but elevated BTM, particularly resorption. More favorable ratios were associated with nutrients from MF and compliance. Younger females had less favorable BTM ratios. Promoting micronutrient intake through compliance with MF may impact bone metabolism in patients with PAH deficiency. SYNOPSIS:Bone mineral density was normal in 44 females with PAH deficiency; however, bone turnover markers suggested uncoupling of bone resorption and formation, particularly in younger patients. Adequate nutrient intake from medical food and overall medical food compliance may positively impact bone turnover.

Project description:Background Phenylalanine hydroxylase (PAH) deficiency is an autosomal recessive disorder that results in elevated concentrations of phenylalanine (Phe) in the blood. If left untreated, the accumulation of Phe can result in profound neurocognitive disability. The objective of this systematic literature review and meta-analysis was to estimate the global birth prevalence of PAH deficiency from newborn screening studies and to estimate regional differences, overall and for various clinically relevant Phe cutoff values used in confirmatory testing. Methods The protocol for this literature review was registered with PROSPERO (International prospective register of systematic reviews). Pubmed and Embase database searches were used to identify studies that reported the birth prevalence of PAH deficiency. Only studies including numeric birth prevalence reports of confirmed PAH deficiency were included. Results From the 85 publications included in the review, 238 birth prevalence estimates were extracted. After excluding prevalence estimates that did not meet quality assessment criteria or because of temporal and regional overlap, estimates from 45 publications were included in the meta-analysis. The global birth prevalence of PAH deficiency, estimated by weighting regional birth prevalences relative to their share of the population of all regions included in the study, was 0.64 (95% confidence interval [CI] 0.53–0.75) per 10,000 births and ranged from 0.03 (95% CI 0.02–0.05) per 10,000 births in Southeast Asia to 1.18 (95% CI 0.64–1.87) per 10,000 births in the Middle East/North Africa. Regionally weighted global birth prevalences per 10,000 births by confirmatory test Phe cutoff values were 0.96 (95% CI 0.50–1.42) for the Phe cutoff value of 360 ± 100 µmol/L; 0.50 (95% CI 0.37–0.64) for the Phe cutoff value of 600 ± 100 µmol/L; and 0.30 (95% CI 0.20–0.40) for the Phe cutoff value of 1200 ± 200 µmol/L. Conclusions Substantial regional variation in the birth prevalence of PAH deficiency was observed in this systematic literature review and meta-analysis of published evidence from newborn screening. The precision of the prevalence estimates is limited by relatively small sample sizes, despite widespread and longstanding newborn screening in much of the world. Supplementary Information The online version contains supplementary material available at 10.1186/s13023-021-01874-6.

Dataset Information

Population genetics of hyperphenylalaninaemia resulting from phenylalanine hydroxylase deficiency in Portugal.

Publications

Population genetics of hyperphenylalaninaemia resulting from phenylalanine hydroxylase deficiency in Portugal.

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