Undiagnosed Phenylketonuria Can Exist Everywhere:Results From an International Survey

Many countries do not have a newborn screening (NBS) program, and immigrants from such countries are at risk for late diagnosis of phenylketonuria (PKU). In this international survey, 52 of 259 patients (20%) with late diagnosed PKU were immigrants, and 145 of the 259 (55%) were born before NBS or in a location without NBS

Molecular genetics of PKU in Poland and potential impact of mutations on BH4 responsiveness

Tetrahydrobiopterin (BH4) has been recently approved as a treatment of patients with phenylketonuria. However, as a confirmation of BH4-responsiveness, it might require a very expensive trial treatment with BH4 or prolonged BH4-loading procedures. The selection of patients eligible for BH4-therapy by means of genotyping of the PAH gene mutations may be recommended as a complementary approach. A population-wide genotyping study was carried out in 1286 Polish phenyloketonuria-patients. The aim was to estimate the BH4 demand and to cover prospectively the treatment by a National Health Fund. A total of 95 types of mutations were identified. Genetic variants corresponding with probable BH4-responsiveness were found in 28.2% of cases. However, patients with mild or classical phenylketonuria who require continuous treatment accounted for 11.4% of the studied population only. Analysis of the published data shows similar percentage of the "BH4-responsive" variants of a PAH gene in patients from other countries of Eastern Europe. Therefore, it can be concluded, that the proportion of phenylketonuria-patients who could benefit from the use of BH4 reaches approximately 10% in the entire region

Bone mineral density is within normal range in most adult phenylketonuria patients

Low bone mineral density (BMD) as a risk factor for fractures has been a long-standing concern in phenylketonuria (PKU). It is hypothesised that the disease itself or the dietary treatment might lead to a low BMD. Previous studies show conflicting results of BMD in PKU due to differences in age, techniques to assess BMD and criteria used. To assess the prevalence of low BMD and define possible risk factors in a large number of adult, early treated PKU (ETPKU) patients. European centres were invited for a survey, collecting retrospective data including results of dual-energy X-ray absorptiometry (DXA) scans of adult ETPKU patients. BMD of 183 adult ETPKU patients aged 18-46 (median age 28, all females premenopausal) years was lower than in the general population at most skeletal sites but the frequency of low BMD (Z-score <−2) was at maximum 5.5%. No risk factors for low BMD in PKU patients could be identified. Low BMD occurs only in a small subset of PKU patients. DXA scans should be considered for well controlled patients from age 35-40 years and up and on indication in those PKU patients considered to be at increased risk for fractures

Mutations in NLRP5 are associated with reproductive wastage and multilocus imprinting disorders in humans

This is the final version. It first appeared at http://www.nature.com/ncomms/2015/150901/ncomms9086/full/ncomms9086.html.Human-imprinting disorders are congenital disorders of growth, development and metabolism, associated with disturbance of parent of origin-specific DNA methylation at imprinted loci across the genome. Some imprinting disorders have higher than expected prevalence of monozygotic twinning, of assisted reproductive technology among parents, and of disturbance of multiple imprinted loci, for which few causative trans-acting mutations have been found. Here we report mutations in NLRP5 in five mothers of individuals affected by multilocus imprinting disturbance. Maternal-effect mutations of other human NLRP genes, NLRP7 and NLRP2, cause familial biparental hydatidiform mole and multilocus imprinting disturbance, respectively. Offspring of mothers with NLRP5 mutations have heterogenous clinical and epigenetic features, but cases include a discordant monozygotic twin pair, individuals with idiopathic developmental delay and autism, and families affected by infertility and reproductive wastage. NLRP5 mutations suggest connections between maternal reproductive fitness, early zygotic development and genomic imprinting.L.E.D. and F.I.R. were supported by the Medical Research Council (MR/J000329/1). J.B., K.B., B.H., L.S. M.B. and T.E. were supported by Bundesministerium fu?r Bildung und Forschung (grant number 01GM1513A and 01GM1513C) and C.T. was supported by an Ipsen Fellowship Grant. The cohort ?Imprinting Disorders-Finding out Why? was accrued through the support of the Newlife Foundation for Disabled Children and through support from the Wessex NIHR clinical research network and NIHR Wellcome Southampton clinical research facility. Funding for DNA collection and methylation analysis of normal control samples was provided in part by the National Institutes of Health R01 AI091905-01, R01 AI061471 and R01 HL082925. ERM thanks Action Medical Research for support

The Genetic Landscape and Epidemiology of Phenylketonuria

Phenylketonuria (PKU), caused by variants in the phenylalanine hydroxylase (PAH) gene, is the most common autosomal-recessive Mendelian phenotype of amino acid metabolism. We estimated that globally 0.45 million individuals have PKU, with global prevalence 1:23,930 live births (range 1:4,500 [Italy]-1:125,000 [Japan]). Comparing genotypes and metabolic phenotypes from 16,092 affected subjects revealed differences in disease severity in 51 countries from 17 world regions, with the global phenotype distribution of 62% classic PKU, 22% mild PKU, and 16% mild hyperphenylalaninemia. A gradient in genotype and phenotype distribution exists across Europe, from classic PKU in the east to mild PKU in the southwest and mild hyperphenylalaninemia in the south. The c.1241A gt G (p.Tyr414Cys)-associated genotype can be traced from Northern to Western Europe, from Sweden via Norway, to Denmark, to the Netherlands. The frequency of classic PKU increases from Europe (56%) via Middle East (71%) to Australia (80%). Of 758 PAH variants, c.1222C gt T (p.Arg408Trp) (22.2%), c.1066-11G gt A (IVS10-11G gt A) (6.4%), and c.782G gt A (p.Arg261Gln) (5.5%) were most common and responsible for two prevalent genotypes: p.[Arg408Trp];[Arg408Trp] (11.4%) and c.[1066-11G gt A];[1066-11G gt A] (2.6%). Most genotypes (73%) were compound heterozygous, 27% were homozygous, and 55% of 3,659 different genotypes occurred in only a single individual. PAH variants were scored using an allelic phenotype value and correlated with pre-treatment blood phenylalanine concentrations (n = 6,115) and tetrahydrobiopterin loading test results (n = 4,381), enabling prediction of both a genotype-based phenotype (88%) and tetrahydrobiopterin responsiveness (83%). This study shows that large genotype databases enable accurate phenotype prediction, allowing appropriate targeting of therapies to optimize clinical outcome

Maternal variants in NLRP and other maternal effect proteins are associated with multilocus imprinting disturbance in offspring

Background: Genomic imprinting results from the resistance of germline epigenetic marks to reprogramming in the early embryo for a small number of mammalian genes. Genetic, epigenetic or environmental insults that prevent imprints from evading reprogramming may result in imprinting disorders, which impact growth, development, behaviour and metabolism. We aimed to identify genetic defects causing imprinting disorders, by whole-exome sequencing in families with one or more members affected by multi-locus imprinting disturbance. Methods: Whole-exome sequencing was performed in 38 pedigrees where probands had multi-locus imprinting disturbance, in five of whom, maternal variants in NLRP5 have previously been found. Results: We now report 15 further pedigrees in which offspring had disturbance of imprinting, while their mothers had rare, predicted-deleterious variants in maternal-effect genes, including NLRP2, NLRP7 and PADI6. As well as clinical features of well-recognised imprinting disorders, some offspring had additional features including developmental delay, behavioural problems and discordant monozygotic twinning, while some mothers had reproductive problems including pregnancy loss. Conclusion: The identification of 20 putative maternal-effect variants in 38 families affected by multi-locus imprinting disorders adds to the evidence that maternal genetic factors affect oocyte fitness and thus offspring development. Testing for maternal-effect genetic variants should be considered in families affected by atypical imprinting disorders.<br/