Undiagnosed maternal phenylketonuria: own clinical experience and literature review

Classical phenylketonuria presenting as maternal PKU syndrome in the offspring of an intellectually normal woman

Phenylketonuria (PKU) is an autosomal recessive inborn error of metabolism resulting from a deficiency of phenylalanine hydroxylase (PAH). If untreated by dietary restriction of phenylalanine intake, impaired postnatal cognitive development results from the neurotoxic effects of excessive phenylalanine (Phe). Signs and symptoms include severe intellectual disability and behavior problems with a high frequency of seizures and variable microcephaly. Maternal PKU syndrome refers to fetal damage resulting in congenital abnormalities when the mother has untreated PKU during pregnancy. Here, we report an intellectually normal 32-year-old female who presented with recurrent pregnancy loss and two neonatal deaths with congenital heart disease, microcephaly, intrauterine growth restriction, and respiratory distress. She was diagnosed with PKU through exome sequencing performed for carrier testing with a homozygous pathogenic variant in the PAH gene, c.169_171del, p.(Glu57del) that is associated with classical PKU. Consistent with the genetic finding, she had a markedly increased plasma phenylalanine concentration of 1642 μmol/L (normal <100). This case demonstrates that recurrent pregnancy loss due to untreated maternal PKU may present as an initial finding in otherwise unsuspected classical PKU and illustrates that extreme degrees of variable expressivity may occur in classical PKU. Moreover, this case illustrates the value of genomic sequencing of women who experience recurrent pregnancy loss or neonatal anomalies.

Neurological and imaging phenotypes of adults with untreated phenylketonuria: new cases and literature review

OBJECTIVES

Phenylketonuria (PKU) is the most prevalent congenital disease of amino acid metabolism. Neurological manifestations usually complicate PKU in untreated adult patients. This study describes neurological and imaging phenotypes of adult patients with untreated PKU.

METHODS

We investigated a cohort of 320 unrelated adult patients with suspected genetic leukoencephalopathies using whole-exome sequencing (WES). We analyzed the phenotypic features of adult PKU patients in our cohort and summarized cases reported in the literature.

RESULTS

We identified 10 patients in our cohort and 12 patients in the literature, who presented with neurological manifestations and were diagnosed with PKU in adulthood. Approximately 60% of these patients had onset of clinical features in adulthood. The most common neurological symptoms of patients presenting in adulthood were cognitive disturbance and spastic paralysis, followed by vision loss, cerebellar ataxia, weakness of limbs, and seizure. This differed from that of patients presenting with PKU features in childhood, who consistently had mental retardation with various neurological complications emerging during a broad age range. Imaging findings were similar between patients presenting with clinical features in childhood compared with adulthood, comprising symmetric periventricular white matter hyperintense on T2-weighted imaging and diffusion-weighted imaging predominantly in the parietal and occipital lobes. Also, normal brain imaging and diffuse leukoencephalopathies were observed in both patient groups.

CONCLUSION

PKU with clinical features presenting in adulthood is an atypical subtype and should be considered during diagnosis of adults with neurological symptoms and leukoencephalopathy. DWI seems to be most helpful to distinguish patients with PKU. Additionally, we demonstrate that PKU constitutes a part (3.1%) of adult genetic leukoencephalopathies.

Rapid and Label-Free Prenatal Detection of Down's Syndrome Using Body Fluid Surface Enhanced Raman Spectroscopy

Down's syndrome (DS) is the leading genetic cause of intellectual disability. In this work, the surface enhanced Raman spectroscopy (SERS) was used for the detection of amniotic fluid and plasma from pregnant women with DS fetus for the first time. High-quality and characteristic spectral features of amniotic fluid and plasma samples from DS groups can be obtained in comparison to normal group. Moreover, principal component analysis with linear discriminant analysis was applied to generate the efficient diagnostic model, achieving accuracies of 94.3% and 88.5% for the DS detection with amniotic fluid and plasma samples, respectively. This preliminary study would provide a novel, convenient and accurate prenatal test based on blood SERS technology for clinical DS screening.

Continuation of pegvaliase treatment during pregnancy: A case report

Phenylalanine hydroxylase (PAH) deficiency is an inborn error of phenylalanine (Phe) metabolism that results in the buildup of dietary Phe to potentially toxic levels. Poorly controlled Phe levels in women of childbearing age are particularly worrisome due to the toxic effect of elevated Phe on fetal development. Pegvaliase was recently approved as an enzyme substitution therapy to reduce Phe concentrations in adult patients with PAH deficiency who have suboptimal Phe control on existing management. During the pegvaliase clinical trials pregnant patients were excluded from participation, but the approved label does not contraindicate its use during pregnancy. This case report describes the outcome of the first PAH deficient patient who elected to continue treatment with pegvaliase during pregnancy and reviews the lessons learned and future considerations.

Intellectual and Developmental Status in Children With Hyperphenylalaninemia and PKU Who Were Screened in a National Program

BACKGROUND

Hyperphenylalaninemia (HPA) and Phenylkeonuria (PKU) are metabolic errors caused by deficiency of phenylalanine hydroxylase enzyme, which results in increased level of phenylalanine. This increase is toxic to the growing brain.

OBJECTIVES

The purpose of this study was to compare the intellectual and developmental status in HPA and PKU children with normal population in national screening program.

PATIENTS AND METHODS

In a historical cohort study, 41 PKU patients who had the inclusion criteria and 41 healthy children were evaluated. Wechsler preschool and primary scale of intelligence-3rd edition (WPPI-3) was used in order to assess the intellectual status of children 4 years and older and Ages and stages questionnaire (ASQ) was used to assess the developmental status of children 5 years and younger.

RESULTS

In intellectual test comparison, the two groups showed significant difference in Wechsler's performance intelligence score and some performance subscales (P-value < 0.01). In comparison of developmental status, no significant difference was observed between the two groups (P-value > 0.05).

CONCLUSIONS

Even with early diagnosis and treatment of PKU patients, these children show some deficiencies intellectually compared to normal children. This study emphasizes on necessity for screening intellectual and developmental status of PKU patients so that effective medical or educational measures can taken in case of deficiencies.

Costs and outcomes over 36 years of patients with phenylketonuria who do and do not remain on a phenylalanine-restricted diet

BACKGROUND

To quantify the costs and consequences of managing phenylketonuria (PKU) in the UK and to estimate the potential implications to the UK's National Health Service (NHS) of keeping patients on a phenylalanine-restricted diet for life.

METHOD

A computer-based model was constructed depicting the management of PKU patients over the first 36 years of their life, derived from patients suffering from this metabolic disorder in The Health Improvement Network database (a nationally representative database of patients registered with general practitioners in the UK). The model was used to estimate the incidence of co-morbidities and the levels of healthcare resource use and corresponding costs over the 36 years.

RESULTS

Patients who remained on a phenylalanine-restricted diet accounted for 38% of the cohort. Forty-seven per cent of patients discontinued their phenylalanine-restricted diet between 15 and 25 years of age. Of these, 73% remained off diet and 27% restarted a restricted diet at a mean 30 years of age. Fifteen per cent of the cohort had untreated PKU. Eleven per cent of patients who remained on a phenylalanine-restricted diet for 36 years received the optimum amount of prescribed amino acid supplements. Patients had a mean 12 general practitioner visits per year and one hospital outpatient visit annually, but phenylalanine levels were only measured once every 18 to 24 months. The mean NHS cost (at 2007/08 prices) of managing a PKU sufferer over the first 36 years of their life was estimated to range between £21 000 and £149 000, depending on the amount of prescribed nutrition they received.

CONCLUSION

The findings suggest that the majority of patients with PKU were under-treated. The NHS cost of patient management should not be an obstacle to encouraging patients to remain on a restricted diet until further information becomes available about the long-term clinical impact of stopping such a diet. Nevertheless, patients require counselling and managed follow up regardless of the choices they make about their diet.

Generation n + 1: Projected numbers of babies born to women with PKU compared to babies with PKU in the United States in 2009

Newborn PKU screening has been available since the mid-1960s, and the first group of screened babies is now a complete reproductive cohort (age 15-44). Untreated maternal PKU (MPKU) often results in significant developmental and physical disabilities in exposed fetuses, and could potentially offset some or all of the benefits produced by newborn PKU screening and dietary treatment. Based on the age distribution of the United States population in 2009, and using different estimates of PKU frequency (1/10,000; 1/15,000; 1/20,000), the projected number of babies born to women with PKU was compared to the projected number of babies born with PKU. In 2009, there were about 62,000,000 women age 15-44, with a fertility rate of 66.7 births/1,000 women. Of these women, depending on the incidence of PKU, 3,097-6,195 were estimated to have PKU, and they would have delivered 207-413 babies. In that same year, the number of births was 4,118,055, which would have resulted in 206-412 babies with PKU. Thus, in the United States, at all estimates of PKU frequency, the number of babies exposed to MPKU is equal to the number of babies born with PKU. This ratio varies with the fertility rate but is not dependent on the incidence of PKU. The benefits of newborn PKU screening and treatment could be significantly curtailed if adequate resources, education, and funding are not available to follow and monitor women with MPKU and their babies.

A newborn with unusual morphology: some practical aspects

Newborns with an unusual phenotype with or without malformations are common in the practice of every paediatrician. Determining whether the phenotype is a variation of normal or should be considered abnormal and, if the latter, also finding the cause can be extremely difficult. Here the main steps that should be followed in the diagnostic procedures are discussed. A careful family history and detailed physical examination remain the hallmarks of the investigations in all newborns. Very frequently clinical photographs will facilitate discussing patients with colleagues. Additional investigations usually include radiological examinations of all body parts that show abnormalities, and screening of the heart, kidneys, eyes and hearing. The studies with the highest yield are cytogenetic analyses which nowadays often involve microarray assays. In the near future, total exome sequencing will be available for diagnostic purposes which will have a major impact on the diagnostic process.