Timing of strict diet in relation to fetal damage in maternal phenylketonuria. An international collaborative study by the MRC/DHSS Phenylketonuria Register

Phenylketonuria and the brain

Classic phenylketonuria (PKU) is caused by defective activity of phenylalanine hydroxylase (PAH), the enzyme that coverts phenylalanine (Phe) to tyrosine. Toxic accumulation of phenylalanine and its metabolites, left untreated, affects brain development and function depending on the timing of exposure to elevated levels. The specific mechanisms of Phe-induced brain damage are not completely understood, but they correlate to phenylalanine levels and on the stage of brain growth. During fetal life, high levels of phenylalanine such as those seen in maternal PKU can result in microcephaly, neuronal loss and corpus callosum hypoplasia. Elevated phenylalanine levels during the first few years of life can cause acquired microcephaly, severe cognitive impairment and epilepsy, likely due to the impairment of synaptogenesis. During late childhood, elevated phenylalanine can cause alterations in neurological functioning, leading to ADHD, speech delay and mild IQ reduction. In adolescents and adults, executive function and mood are affected, with some of the abnormalities reversed by better control of phenylalanine levels. Altered brain myelination can be present at this stage. In this article, we review the current knowledge about the consequences of high phenylalanine levels in PKU patients and animal models through different stages of brain development and its effect on cognitive, behavioural and neuropsychological function.

Neurotoxicity of phenylalanine on human iPSC-derived cerebral organoids

Phenylketonuria (PKU) is a common genetic metabolic disorder that causes phenylalanine accumulation in the blood. The most serious symptoms are related to the brain, as intellectual disability, seizure, and microcephaly are commonly found in poorly treated PKU patients and the babies of maternal PKU. However, the mechanism of hyperphenylalaninemia on human neurodevelopment is still unclear. Here we utilized human induced pluripotent stem cell (iPSC)-derived cerebral organoids to investigate the neurotoxicity of hyperphenylalaninemia. Cerebral organoids at days 40 or 100 were treated with different concentrations of phenylalanine for 5 days. After phenylalanine treatments, the cerebral organoids displayed alterations in organoid size, induction of apoptosis, and depletion of neural progenitor cells. However, phenylalanine did not have an impact on neurons and glia, including astrocytes, immature oligodendrocytes, and mature oligodendrocytes. Remarkably, a reduction in the thickness of the cortical rosettes and a decrease in myelination at the intermediate zone were inspected with the elevated phenylalanine concentrations. RNA-seq of phenylalanine-treated organoids revealed that gene sets related to apoptosis, p53 signaling pathway, and TNF signaling pathway via NF-kB were enriched in upregulated genes, while those related to cell cycle and amino acid metabolism were enriched in downregulated genes. In addition, there were several microcephaly disease genes, such as ASPM, LMNB1, and CENPE, ranked at the top of the downregulated genes. These findings indicate that phenylalanine exposure may contribute to microcephaly, abnormal cortical expansion, and myelination lesions in the developing human brain.

Phenylketonuria

Phenylketonuria (PKU; also known as phenylalanine hydroxylase (PAH) deficiency) is an autosomal recessive disorder of phenylalanine metabolism, in which especially high phenylalanine concentrations cause brain dysfunction. If untreated, this brain dysfunction results in severe intellectual disability, epilepsy and behavioural problems. The prevalence varies worldwide, with an average of about 1:10,000 newborns. Early diagnosis is based on newborn screening, and if treatment is started early and continued, intelligence is within normal limits with, on average, some suboptimal neurocognitive function. Dietary restriction of phenylalanine has been the mainstay of treatment for over 60 years and has been highly successful, although outcomes are still suboptimal and patients can find the treatment difficult to adhere to. Pharmacological treatments are available, such as tetrahydrobiopterin, which is effective in only a minority of patients (usually those with milder PKU), and pegylated phenylalanine ammonia lyase, which requires daily subcutaneous injections and causes adverse immune responses. Given the drawbacks of these approaches, other treatments are in development, such as mRNA and gene therapy. Even though PAH deficiency is the most common defect of amino acid metabolism in humans, brain dysfunction in individuals with PKU is still not well understood and further research is needed to facilitate development of pathophysiology-driven treatments.

Maternal PKU: Defining phenylalanine tolerance and its variation during pregnancy, according to genetic background

BACKGROUND AND AIMS

Phenylketonuria (PKU)-affected women may become pregnant, and dietary phenylalanine (Phe) intake must be adjusted according to Phe tolerance. We report our experience with maternal PKU in relation to genotype PKU heterogeneity.

METHODS AND RESULTS

A total of 10 pregnancies in 7 PKU women (7 different genotypes) were followed up as part of personalized care. Phe tolerance during preconception and pregnancy was assessed by strict dietary control and weekly Phe measurement (blood spots) in relation to genotype. Most women had stopped PKU diet during childhood or adolescence and six pregnancies were unplanned; a phenylalanine-restricted diet was reinstituted soon after conception. Women were classified according to their Phe levels at birth screening and genotype. Phe tolerance increased systematically in the course of pregnancy in all cases, but the increase was different in subjects with classic PKU (cPKU) when compared with cases with mild hyperphenylalaninemia (mHPA), both on average (+297 mg/day in cPKU vs. 597 in mHPA; P = 0.017) and as percentage (+107% in cPKU vs. +17% in mHPA). Notably, Phe tolerance also varied in the same women in the course of different pregnancies, when body weight gain was also different. Two newborns from the same cPKU mother (unplanned pregnancies on free diet) were affected by congenital alterations.

CONCLUSIONS

Several factors influence metabolic phenotype in maternal PKU, to an unpredictable extent even in the same woman. The number of maternal PKU cases is growing in dedicated Nutrition Units, and the burden associated with careful management of this condition for the health care system should be adequately considered.

First Japanese case of maternal phenylketonuria treated with sapropterin dihydrochloride and the normal growth and development of the child

Sapropterin dihydrochloride (SD) may be a new treatment option for women with phenylketonuria (PKU) who plan to become pregnant. We report the first Japanese case of maternal PKU treated with SD. The patient was administered SD at 10-20 mg/kg/day, which increased phenylalanine tolerance during the pregnancy and lactation. No adverse events occurred, and she delivered a healthy neonate. Normal growth and development of the child confirms the efficacy and safety of SD.

Preconception healthcare and congenital disorders: systematic review of the effectiveness of preconception care programs in the prevention of congenital disorders

Congenital disorders are a leading cause of global burden of disease; the birth prevalence remains constant at 6%. Initiating preconception care before pregnancy may be an effective strategy to reduce congenital disorders and improve the health of reproductive-age women. Our objectives are: (1) To identify components of preconception interventions, (2) to assess the effectiveness of preconception interventions in reducing the burden of congenital disorders, and (3) to prioritize these interventions. Medline and Science Direct search terms included: preconception, pre-pregnancy, childbearing, reproduction, care, intervention, primary care, healthcare, model, program, prevention, trial, efficacy, effectiveness, congenital disorders OR abnormalities. Inclusion criteria were: (1) English, (2) human subjects, (3) women of childbearing age, (4) 1980-current data, (5) all countries, (6) experimental studies, (7) systematic reviews or meta-analysis, (8) program reports/evaluations. Data was collected and abstracted by two independent reviewers. To prioritize preconception interventions likely to have the largest impact at a population level, a ranked scoring system was created incorporating the following: (1) quality of evidence supporting the intervention, (2) effect size of the intervention, and (3) global burden of the specific congenital disease. Preconception interventions include risk screening, education, motivational counseling, disease optimization and specialist referral. The most effective interventions, based on the strength of evidence, size of impact of intervention, and disease burden are: folic acid fortification/supplementation, diabetic control, smoking and alcohol interventions, HIV management, thrombophillia screening, obesity prevention and epilepsy management. Although multiple conditions require preconception attention, only nine interventions have evidence to support their effect on congenital disorders through a randomised control trial, systematic review or meta-analysis. There is a need for more high-level research in evaluating certain preconception interventions. These findings have significant implications on planning and implementation of preconception care.

Preconception care: screening and management of chronic disease and promoting psychological health

INTRODUCTION

A large proportion of women around the world suffer from chronic diseases including mental health diseases. In the United States alone, over 12% of women of reproductive age suffer from a chronic medical condition, especially diabetes and hypertension. Chronic diseases significantly increase the odds for poor maternal and newborn outcomes in pregnant women.

METHODS

A systematic review and meta-analysis of the evidence was conducted to ascertain the possible impact of preconception care for preventing and managing chronic diseases and promoting psychological health on maternal, newborn and child health outcomes. A comprehensive strategy was used to search electronic reference libraries, and both observational and clinical controlled trials were included. Cross-referencing and a separate search strategy for each preconception risk and intervention ensured wider study capture.

RESULTS

Maternal prepregnancy diabetic care is a significant intervention that reduces the occurrence of congenital malformations by 70% (95% Confidence Interval (CI): 59-78%) and perinatal mortality by 69% (95% CI: 47-81%). Furthermore, preconception management of epilepsy and phenylketonuria are essential and can optimize maternal, fetal and neonatal outcomes if given before conception. Ideally changes in antiepileptic drug therapy should be made at least 6 months before planned conception. Interventions specifically targeting women of reproductive age suffering from a psychiatric condition show that group-counseling and interventions leading to empowerment of women have reported non-significant reduction in depression (economic skill building: Mean Difference (MD) -7.53; 95% CI: -17.24, 2.18; counseling: MD-2.92; 95% CI: -13.17, 7.33).

CONCLUSION

While prevention and management of the chronic diseases like diabetes and hypertension, through counseling, and other dietary and pharmacological intervention, is important, delivering solutions to prevent and respond to women's psychological health problems are urgently needed to combat this leading cause of morbidity.

Preconception care: delivery strategies and packages for care

The notion of preconception care aims to target the existing risks before pregnancy, whereby resources may be used to improve reproductive health and optimize knowledge before conceiving. The preconception period provides an opportunity to intervene earlier to optimize the health of potential mothers (and fathers) and to prevent harmful exposures from affecting the developing fetus. These interventions include birth spacing and preventing teenage pregnancy, promotion of contraceptive use, optimization of weight and micronutrient status, prevention and management of infectious diseases, and screening for and managing chronic conditions. Given existing interventions and the need to organize services to optimize delivery of care in a logical and effective manner, interventions are frequently co-packaged or bundled together. This paper highlights packages of preconception interventions that can be combined and co-delivered to women through various delivery channels and provides a logical framework for development of such packages in varying contexts.

Clinical genomic database

Technological advances have greatly increased the availability of human genomic sequencing. However, the capacity to analyze genomic data in a clinically meaningful way lags behind the ability to generate such data. To help address this obstacle, we reviewed all conditions with genetic causes and constructed the Clinical Genomic Database (CGD) (http://research.nhgri.nih.gov/CGD/), a searchable, freely Web-accessible database of conditions based on the clinical utility of genetic diagnosis and the availability of specific medical interventions. The CGD currently includes a total of 2,616 genes organized clinically by affected organ systems and interventions (including preventive measures, disease surveillance, and medical or surgical interventions) that could be reasonably warranted by the identification of pathogenic mutations. To aid independent analysis and optimize new data incorporation, the CGD also includes all genetic conditions for which genetic knowledge may affect the selection of supportive care, informed medical decision-making, prognostic considerations, reproductive decisions, and allow avoidance of unnecessary testing, but for which specific interventions are not otherwise currently available. For each entry, the CGD includes the gene symbol, conditions, allelic conditions, clinical categorization (for both manifestations and interventions), mode of inheritance, affected age group, description of interventions/rationale, links to other complementary databases, including databases of variants and presumed pathogenic mutations, and links to PubMed references (>20,000). The CGD will be regularly maintained and updated to keep pace with scientific discovery. Further content-based expert opinions are actively solicited. Eventually, the CGD may assist the rapid curation of individual genomes as part of active medical care.

Phenylalanine hydroxylase deficiency

Phenylalanine hydroxylase deficiency is an autosomal recessive disorder that results in intolerance to the dietary intake of the essential amino acid phenylalanine. It occurs in approximately 1:15,000 individuals. Deficiency of this enzyme produces a spectrum of disorders including classic phenylketonuria, mild phenylketonuria, and mild hyperphenylalaninemia. Classic phenylketonuria is caused by a complete or near-complete deficiency of phenylalanine hydroxylase activity and without dietary restriction of phenylalanine most children will develop profound and irreversible intellectual disability. Mild phenylketonuria and mild hyperphenylalaninemia are associated with lower risk of impaired cognitive development in the absence of treatment. Phenylalanine hydroxylase deficiency can be diagnosed by newborn screening based on detection of the presence of hyperphenylalaninemia using the Guthrie microbial inhibition assay or other assays on a blood spot obtained from a heel prick. Since the introduction of newborn screening, the major neurologic consequences of hyperphenylalaninemia have been largely eradicated. Affected individuals can lead normal lives. However, recent data suggest that homeostasis is not fully restored with current therapy. Treated individuals have a higher incidence of neuropsychological problems. The mainstay of treatment for hyperphenylalaninemia involves a low-protein diet and use of a phenylalanine-free medical formula. This treatment must commence as soon as possible after birth and should continue for life. Regular monitoring of plasma phenylalanine and tyrosine concentrations is necessary. Targets of plasma phenylalanine of 120-360 μmol/L (2-6 mg/dL) in the first decade of life are essential for optimal outcome. Phenylalanine targets in adolescence and adulthood are less clear. A significant proportion of patients with phenylketonuria may benefit from adjuvant therapy with 6R-tetrahydrobiopterin stereoisomer. Special consideration must be given to adult women with hyperphenylalaninemia because of the teratogenic effects of phenylalanine. Women with phenylalanine hydroxylase deficiency considering pregnancy should follow special guidelines and assure adequate energy intake with the proper proportion of protein, fat, and carbohydrates to minimize risks to the developing fetus. Molecular genetic testing of the phenylalanine hydroxylase gene is available for genetic counseling purposes to determine carrier status of at-risk relatives and for prenatal testing.

Disease registries and outcomes research in children: focus on lysosomal storage disorders

Assessing medicines specifically for use in children has been neglected in the past, with the majority of formal clinical studies being conducted in adults. Clinical trials are a pivotal part of the drug approval process; however, they are not always applicable to the diverse populations - including children - that receive the drug after approval. They may not be the most informative assessment tool, especially in rare (or orphan) disorders where there are few patients, due to a lack of existing natural history data and the challenges of designing appropriately powered statistical analyses. Disease registries, which can collect clinical information in larger, more heterogeneous populations than can be included in a clinical trial, are becoming increasingly valuable. Their use is particularly beneficial for diseases affecting very small patient populations, such as lysosomal storage disorders (LSDs), and for looking at specific populations, for example, children. Such disease registries can provide natural history data as well as enable the impact of therapy to be examined. Moreover, despite potential limitations of enrollment bias and unmonitored data, patient registries can play a valuable role in assuring pediatric health, providing longitudinal data that can be used to monitor developmental outcomes in chronic lifelong diseases, and assessing the effectiveness of treatment. This review describes the role of registries in drug development and regulatory approval, the impact of global registry programs on pediatric research, with some examples from the field of LSDs, and how registries are impacting the clinical care such children receive.

The clinical content of preconception care: women with chronic medical conditions

This article reviews the medical conditions that are associated with adverse pregnancy outcomes for women and their offspring. We also present the degree to which specific preconception interventions and treatments can impact the effects of the condition on birth outcomes. Because avoiding, delaying, or achieving optimal timing of a pregnancy is often an important component of the preconception care of women with medical conditions, contraceptive considerations particular to the medical conditions are also presented.

Phenylketonuria: questioning the gospel

Phenylketonuria (PKU) was first described over 70 years ago, treatment was developed 50 years ago and universal newborn PKU screening was introduced 40 years ago. Phenylalanine-restricted dietary treatment has prevented mental retardation in thousands of individuals worldwide. We acknowledge, however, that there is still much to learn in the field. The incidence of mental retardation in untreated PKU is likely to be considerably less than the original estimates. Since dietary control is suboptimal in late childhood, adolescence and adulthood, alternative methods of treatment are being explored. These include large neutral amino acids, phenylalanine ammonia lyase, tetrahydrobiopterin and gene replacement. Evidence has surfaced that the semisynthetic, low-protein diet used to treat PKU may be deficient in certain important nutrients. Maternal PKU treatment may be successful even if initiated as late as 8-10 weeks into pregnancy. A plea is made for the immediate establishment of adult treatment centers for PKU (and other inherited metabolic diseases) for long-term treatment, follow-up and research.

Impaired glutamatergic synaptic transmission in the PKU brain

This paper reviews recent results of our investigation of the mechanisms whereby hyperphenylalaninemia may cause brain dysfunction in classical phenylketonuria (PKU). Acute applications of L-Phe in rat and mouse hippocampal and cerebrocortical cultured neurons, at a range of concentrations found in PKU brain, significantly and reversibly depressed glutamatergic synaptic transmission by a combination of pre- and postsynaptic actions: (1) competition for the glycine-binding site of the N-methyl-D-aspartate (NMDA) receptors; (2) attenuation of neurotransmitter release; (3) competition for the glutamate-binding site of (RS)-amino-3-hydroxy-5-methyl-4-isoxazolepropioinic acid and kainate (AMPA/kainate) receptors. Unlike L-Phe, its non-tyrosine metabolites, phenylacetic acid, phenylpyruvic acid, and phenyllactic acid, did not produce antiglutamatergic effects. L-Phe did not affect inhibitory gamma-aminobutyric (GABA)-ergic transmission. Consistent with this specific pattern of effects caused by L-Phe in neuronal cultures, the expression of NMDA receptor NR2A and AMPA receptor Glu1 and Glu2/3 subunits in brain of hyperphenylalaninemic PKU mice (Pah(enu2) strain) was significantly increased, whereas expression of the NMDA receptor NR2B subunit was decreased. There was no change in GABA alpha1 subunit expression. Considering the important role of glutamatergic synaptic transmission in normal brain development and function, these L-Phe-induced changes in glutamatergic synaptic transmission in PKU brain may be a critical element of the neurological symptoms of PKU.

Maternal Phenylketonuria Collaborative Study (MPKUCS)--the 'outliers'

Analysis of outcome data from 305 of the 414 offspring from the Maternal Phenylketonuria Collaborative Study (MPKUCS), plus 70 control offspring, revealed significant deficits in the IQ (intelligence quotient), as measured by the Wechsler Intelligence Scale for Children--Revised (WISC-R), when maternal metabolic control during pregnancy was delayed and/or inadequate. There were, however, 23 'outliers' (7.5% of the 305) in which the offspring's intellectual IQ was worse (n =10) or better (n =13) than expected. The aim of this study was to determine whether collection parameters were incomplete or whether these subjects were true biological variants influenced by other undetected factors or, perhaps, by modifier genes. Among the 10 offspring whose intellectual functioning was worse than expected, additional complications were uncovered that could explain the poor outcome. Four of the 13 offspring with higher than expected IQ had mothers with mild variants of PKU in which the insult to the fetus would not be expected to be as profound. For the other nine offspring whose intellectual performance was better than expected, there was no explanation, based on the parameters studied. We hypothesize that modifier genes will, at times, protect the fetus despite high maternal concentrations of phenylalanine. Not all offspring from the same (untreated) PKU mother may be similarly affected. Finding the source of these modifiers might effect the treatment of MPKU.

Maternal phenylketonuria in Western Australia: pregnancy outcomes and developmental outcomes in offspring

OBJECTIVE

To examine the outcomes of phenylketonuric (PKU) pregnancies in Western Australia including birth characteristics and cognitive and behavioural outcomes in offspring.

METHODS

A cross-sectional study of women and their offspring who were identified from the Western Australian Maternal PKU Program (WAMPKUP) from 1991 to 2000 was carried out. Cognitive assessments (K-BIT or Griffiths scales) were conducted on women and their children, and behavioural assessments (CBCL) were conducted on the children.

RESULTS

Thirty pregnancies by nine women were registered on the WAMPKUP between 1991 and 2000. There were 16 live births, with one preterm delivery at 32 weeks. There were no congenital abnormalities. Five of the nine mothers and their nine children (aged 18 months-10 years) participated in developmental assessments. A linear relationship was shown between lower maternal IQ scores and later attainment of metabolic control in pregnancy (rs = -0.828; P = 0.01). There was significant correlation between lower offspring IQ scores and later attainment of metabolic control in pregnancy (rs = -0.734; P = 0.02). Correlation between maternal and offspring cognitive scores was not significant. Four of nine (44%) children rated in the clinical range for behavioural problems. Compared to children with no behavioural difficulties, these children had lower cognitive abilities (P = 0.05) and maternal metabolic control during pregnancy was poor (P = 0.05).

CONCLUSIONS

Poor metabolic control in pregnancy is associated with poorer cognitive outcomes and increased behavioural difficulties in offspring of mothers with PKU. The results have implications for the implementation of appropriate dietary measures before conception in PKU pregnancies, and indicate a need for the establishment of multidisciplinary teams to follow up individuals with PKU to communicate the importance of pregnancy planning, to manage PKU pregnancies, and to follow up the offspring.

Barriers to successful dietary control among pregnant women with phenylketonuria

PURPOSE

The teratogenic effects of maternal PKU are preventable, yet affected babies continue to be born. This study's purpose was to identify barriers to successful dietary control among pregnant women with PKU.

METHODS

An interview-based study was conducted of women with PKU who were known to metabolic disease clinics in three states and pregnant during 1998 to 2000. Medical records were used to document timing of metabolic control.

RESULTS

Of 24 women in the study, only 8 (33%) initiated the diet before pregnancy. Of 22 medical records received, only 12 (55%) indicated control of blood phenylalanine levels before 10 weeks' gestation. Risk factors for late dietary control included young age and belief that treatment costs complicated the diet. Although all of the women expressed confidence in the metabolic clinic staff, few perceived their obstetricians were knowledgeable about the maternal PKU diet. Of 13 women enrolled in state-based assistance programs, 9 (69%) reported proof of pregnancy was required for eligibility. Many women using private insurance reported their insurers were unwilling to pay for medical foods. When the data were stratified according to state of residence, differences were observed in the rate of live-born infants, prepregnancy medical food use, average travel time to the metabolic clinic, and gestational week when metabolic control was achieved.

CONCLUSION

Our study's findings may be used to target educational messages to women with PKU and to direct future research directions. For example, obstetric knowledge of maternal PKU needs further evaluation. Discrepancies should be resolved between maternal PKU medical recommendations and the policies of third party-payers. The disparities in financial assistance and services available to pregnant women with PKU residing in different states should be examined further.

Importance of diet in maternal phenylketonuria

Diet has long been recognized as the primary treatment modality for individuals with phenylketonuria (PKU) during infancy and childhood. Recent findings from the Maternal PKU Collaborative Study clearly indicate that dietary restriction of phenylalanine is also necessary to prevent the adverse effects of an elevated plasma phenylalanine concentration during pregnancy, which include microcephaly, physical anomalies, and mental retardation.

The international study of pregnancy outcome in women with maternal phenylketonuria: report of a 12-year study

OBJECTIVE

The purpose of this report was to update the results of the Maternal Phenylketonuria Collaborative Study, which was established to assess the efficacy of a phenylalanine-restricted diet in preventing morbidity among the offspring of women with hyperphenylalaninemia.

STUDY DESIGN

During a 12-year period 576 women with hyperphenylalaninemia were enrolled in this study. Outcome measures were stratified according to classification of maternal hyperphenylalaninemia and the time at which dietary control of phenylalanine level was achieved.

RESULTS

Optimal physical and cognitive fetal outcomes occurred when maternal blood phenylalanine level <600 micromol/L was achieved by 8 to 10 weeks' gestation and maintained throughout pregnancy (trimester average, </=600 micromol/L).

CONCLUSIONS

The achievement of blood phenylalanine level control through a phenylalanine-restricted diet significantly diminished the occurrence of congenital abnormalities among offspring of women with hyperphenylalaninemia and improved early intellectual progress of these offspring.

Maternal phenylketonuria: a continuing problem

OBJECTIVES

To estimate the number of women of childbearing age in New South Wales whose children are at risk of the maternal phenylketonuria (PKU) syndrome (intellectual disability, microcephaly, congenital malformations).

SETTING

New South Wales, 1996.

DESIGN

Comparison of number of women with PKU aged 15-44 years on the NSW PKU database (observed number) with expected number derived from population data.

MAIN OUTCOME MEASURES

Observed and expected numbers of women with PKU (defined as blood phenylalanine levels > or = 400 mumol/L, and phenylalanine-restricted diet recommended) by age; number with no clinical contact with the PKU service in previous year; outcomes of pregnancies in women with PKU (January 1994 to July 1996).

RESULTS

110 women aged 15-44 years with PKU were listed on the database. The expected number was 145 (95% confidence interval, 122-171). The difference was greatest in the 30-44 years age group (born before comprehensive newborn screening), with only 55% of the expected number listed. Sixteen women who had been diagnosed with PKU at birth were not having regular follow-up, while 18 women had been diagnosed only after investigation of abnormalities in their children. Of 28 pregnancies managed by the NSW PKU service, 19 were considered unaffected by the maternal PKU syndrome and five affected (another three did not reach term; one outcome was unknown). Of 46 unmanaged pregnancies, all were affected.

CONCLUSION

There is an urgent need for better follow-up of women with PKU and for education of health professionals about the MPKU syndrome, its recognition, the risks of untreated pregnancy and the benefits of dietary treatment.

The Resource Mothers Program for Maternal Phenylketonuria

OBJECTIVES

The purpose of this study was to measure the effectiveness of resource mothers in reducing adverse consequences of maternal phenylketonuria.

METHODS

Nineteen pregnancies in the resource mothers group were compared with 64 pregnancies in phenylketonuric women without resource mothers. Weeks to metabolic control and offspring outcome were measured.

RESULTS

Mean number of weeks to metabolic control was 8.5 (SE = 2.2) in the resource mothers group, as compared with 16.1 (SE = 1.7) in the comparison group. Infants of women in the resource mothers group had larger birth head circumferences and higher developmental quotients.

CONCLUSIONS

The resource mothers program described here improves metabolic control in pregnant women with phenylketonuria.

Effects of dietary mixtures of amino acids on fetal growth and maternal and fetal amino acid pools in experimental maternal phenylketonuria

BACKGROUND

Branched-chain amino acids have been reported to improve fetal brain development in a rat model in which maternal phenylketonuria (PKU) is induced by the inclusion of an inhibitor of phenylalanine hydroxylase, DL-p-chlorophenylalanine, and L-phenylalanine in the diet.

OBJECTIVE

We studied whether a dietary mixture of several large neutral amino acids (LNAAs) would improve fetal brain growth and normalize the fetal brain amino acid profile in a rat model of maternal PKU induced by DL-alpha-methylphenylalanine (AMPhe).

DESIGN

Long-Evans rats were fed a basal diet or a similar diet containing 0.5% AMPhe + 3.0% L-phenylalanine (AMPhe + Phe diet) from day 11 until day 20 of gestation in experiments to test various mixtures of LNAAs. Maternal weight gains and food intakes to day 20, fetal body and brain weights at day 20, and fetal brain and fetal and maternal plasma amino acid concentrations at day 20 were measured.

RESULTS

Concentrations of phenylalanine and tyrosine in fetal brain and in maternal and fetal plasma were higher and fetal brain weights were lower in rats fed the AMPhe + Phe diet than in rats fed the basal diet. However, fetal brain growth was higher and concentrations of phenylalanine and tyrosine in fetal brain and in maternal and fetal plasma were lower in rats fed the AMPhe + Phe diet plus LNAAs than in rats fed the diet containing AMPhe + Phe alone.

CONCLUSION

LNAA supplementation of the diet improved fetal amino acid profiles and alleviated most, but not all, of the depression in fetal brain growth observed in this model of maternal PKU.

New approaches to the treatment of phenylketonuria

Phenylketonuria (PKU) is the most common of all aminoacidopathies and is caused by autosomal recessive deficiency of the hepatic phenylalanine hydroxylase system. The diagnosis of PKU should be multifactorial and based on a protein overload test that reveals increased plasma phenylalanine levels during the ingestion of a normal diet, a phenylalanine tolerance test, and in vitro and in vivo activity of the liver enzyme. An individualized diagnosis that characterizes the severity of the disease in each patient provides objective and effective criteria for the dietary treatment of each particular case.

Social factors and the meaning of food in adherence to medical diets: results of a maternal phenylketonuria summer camp

A Maternal PKU camp provided education and social support for 25 young women with phenylketonuria (PKU). Questionnaires were administered and blood samples were collected on the first and last days of camp to evaluate the psychological and medical impact of the programme. Long-term outcome was assessed through telephone interviews 7-14 months later. Knowledge of maternal PKU and the maternal PKU diet increased significantly. There was a significant increase in campers' ratings of the degree to which others supported the use of birth control to prevent late-treated pregnancies, although campers' comfort with contraception did not change. Mean blood phenylalanine concentrations were significantly reduced by 37% during camp and by 20% at follow-up. Ninety-six per cent of campers remained in contact with other campers after the summer. At follow-up, one pregnancy was reported, in which metabolic control was achieved prior to conception. Overall, attitudes about treatment and perceptions about ability to cope with PKU did not change to a significant degree. It is suggested that camps may be most successful in changing both behaviour and attitudes if they actively involve the campers in food preparation, address the psychological meaning of food in our culture, and provide social support.

Preconception genetic counseling

The purpose of this chapter has not been to be all-inclusive, but to raise awareness of the benefits of preconception consultation in the prevention of birth defects. If there is to be a significant decrease in the incidence of congenital malformations, it will come only by intervention that occurs prior to organogenesis, and that opportunity is lost by the first prenatal visit. For the practitioner interested in a more in-depth analysis of the subject of preconception counseling, the two books listed as supplementary reading provide a wealth of information essential to the care of the patient planning a pregnancy.

Maternal non-phenylketonuric mild hyperphenylalaninemia

Unlike maternal phenylketonuria (PKU) which produces severe birth defects when untreated during pregnancy, maternal non-PKU mild hyperphenylalaninemia (MHP) has a less severe impact but whether it is benign or may have long-term consequences for offspring has been unclear. From an international survey of maternal MHP we obtained information about 86 mothers (blood phenylalanine (Phe) 150-720 mumol/l), their 219 untreated pregnancies and 173 offspring. Spontaneous fetal loss and congenital anomalies were no more frequent than normally expected. Median Z-scores for birth length and birth head circumference and offspring IQ (100), however, were significantly lower for maternal Phe > 400 mumol/l than for maternal Phe < 400 mumol/l, in which the median offspring IQ was 108. Data on maternal MHP from the prospective Maternal PKU Collaborative Study (MPKUCS) are as yet incomplete but seem to be conforming to the general pattern of the international survey. We conclude that maternal blood Phe levels above 400 mumol/l in maternal MHP are associated with lower birth measurements and slightly lower offspring IQ. It would seem that dietary intervention to lower the maternal Phe levels to below 400 mumol/l might be indicated in maternal MHP pregnancies with the higher blood Phe levels.

Maternal phenylketonuria: a metabolic teratogen

The maternal phenylketonuria (PKU) syndrome refers to the teratogenic effects of PKU during pregnancy. These effects include mental retardation, microcephaly, congenital heart disease, and intrauterine growth retardation. In untreated pregnancies wherein the mother has classic PKU with a blood phenylalanine level > or = 1,200 microM (20 mg/dl), the frequencies of these abnormalities in offspring are exceedingly high, approaching 75-90% for microcephaly and mental retardation and 15% for congenital heart disease. There is a dose response relationship with progressively lower frequencies of these abnormalities at lower phenylalanine levels, both in the pregnancies of women with variants of PKU and in treated classic PKU pregnancies. The pathogenesis of this syndrome is unknown; it may be related to inhibition by phenylalanine of large neutral amino acid transport across the placenta or to direct toxicity of phenylalanine and/or a phenylalanine metabolite in certain fetal organs. A mouse model for PKU now exists, and studies of maternal PKU in this model are in progress. The treatment of maternal PKU consists of biochemical control through a phenylalanine restricted diet during pregnancy. The best results are obtained with diet initiation before conception or no later than the earliest weeks of pregnancy. Women with PKU and their families require much psychosocial support to meet the strict requirements of a maternal PKU pregnancy, including compliance with a difficult diet. With such compliance, however, it seems that bearing normal or near normal offspring is possible.

Psychosocial factors in maternal phenylketonuria: women's adherence to medical recommendations

OBJECTIVES

This study identified factors predicting adherence to medical recommendations in maternal phenylketonuria, which can result in severe fetal damage.

METHODS

Sixty-nine women with phenylketonuria, 68 of their acquaintances, and 69 women with diabetes mellitus were interviewed annually for 5 years. A model in which each stage in the maternal phenylketonuria life cycle represented a treatment-related goal provided a means to assess adherence.

RESULTS

At the stages of prevention of unplanned pregnancy, treatment initiation, and diet continuation throughout pregnancy, attitudes and social support were associated with adherence to medical recommendations. No specific variables were associated with outcome at reproductive decision making, but women with phenylketonuria were more likely to delay making a decision, resulting in unplanned and, hence, untreated or late-treated pregnancy.

CONCLUSIONS

Women with phenylketonuria differed from their acquaintances and diabetic women in many respects, suggesting that special programs are needed. Greater emphasis on reproductive decision making is especially needed. Interventions that focus on improving social support networks and attitudes about treatment may increase adherence to recommendations.

Maternal mild hyperphenylalaninaemia: an international survey of offspring outcome

Maternal phenylketonuria (PKU) has adverse effects on the offspring including microcephaly, mental retardation, congenital heart disease, and intrauterine growth retardation. Maternal non-PKU mild hyperphenylalaninaemia (MHP) is believed to be benign, but whether there may be long-term consequences to offspring is unclear. In an international survey we have obtained information about 86 mothers with MHP (blood phenylalanine 167-715 mumol/L), their 219 untreated pregnancies, and 173 offspring. Spontaneous fetal loss (13% of pregnancies), congenital heart disease (2.3% of offspring), and severe non-cardiac anomalies (2.9% of offspring) occurred at frequencies within expected limits for the general population. For weight and length at birth the median percentile was the 50th but that for birth head circumference was the 25th. Median z-scores for birth length and head circumference were significantly lower for offspring of mothers with phenylalanine concentrations above 400 mumol/L than for those whose mothers had lower values (p = 0.05 and p = 0.005, respectively). The median intelligence quotient (IQ) of the offspring (3-27 years) was 100 for those whose mothers had higher phenylalanine concentrations and 108 for those of the lower phenylalaninaemia group. However, offspring IQ correlated slightly more closely with maternal IQ (r = 0.53, p < 0.001) than with maternal phenylalanine concentration (r = 0.45, p = 0.02). Maternal MHP does not seem to have serious consequences for the fetus. A maternal phenylalanine concentration of less than 400 mumol/L does not warrant intervention. Nevertheless, maternal blood phenylalanine above this value is associated with slightly lower birth measurements and offspring IQ than lower maternal blood phenylalanine concentrations.

PKU in adolescents: rationale and psychosocial factors in diet continuation

Follow-up of early-treated children with PKU has shown that diet discontinuation in childhood presents risks of cognitive and emotional dysfunction in a substantial number of adolescents and young adults. This dysfunction includes IQ loss, mental processing abnormalities, learning difficulties, anxiety and personality disorders. In addition, neurologic deterioration has been reported in several such individuals. As a consequence of this current understanding of PKU, diet continuation, at least through adolescence and in the young adult years, is now recommended. Many centers are extending this to a policy of "diet for life". This represents a major challenge to adolescents and their families. Metabolic control using the criteria applied during childhood is virtually impossible to achieve past 12 years of age. Time constraints, social pressures, financial limitations and growing independence from the family combine to interfere with dietary control. Added to these difficulties are the biological changes during teenage years which reduce phenylalanine tolerance. To meet these challenges, we have identified a number of psychosocial factors that interfere with adherence to medical recommendations. The factors most highly related to metabolic control were social support for the diet and positive perceptions of treatment. This information has led to the development of support programs for adolescents and young adults with PKU.(ABSTRACT TRUNCATED AT 250 WORDS)

The international collaborative study of maternal phenylketonuria: status report 1994

Neonatal screening for phenylketonuria (PKU) has created a problem as females with PKU are reaching child-bearing age. Surveys have revealed that maternal phenylalanine blood concentrations greater than 1200 mumol/l are associated with fetal microcephaly, congenital heart defects and intrauterine growth retardation. It is estimated that as many as 3000 hyperphenylalaninemic females may be at risk of producing these fetal abnormalities. To examine this problem, the international maternal PKU collaborative study was developed to evaluate the efficacy of a phenylalanine-restricted diet in reducing fetal morbidity. Preliminary findings have indicated that phenylalanine restriction should begin before conception for females with PKU planning a pregnancy. Dietary control should maintain maternal blood phenylalanine levels between 120 and 360 mumol/l and should provide adequate energy, protein, vitamin and mineral intake. Pregnant hyperphenylalaninemic females who achieved metabolic control after conception or by the 10th week of pregnancy had a better offspring outcome than anticipated. The results of 402 pregnancies are reviewed.

Maternal mild hyperphenylalaninemia: results of treated and untreated pregnancies in two sisters

The outcomes of mild hyperphenylalaninemia (MHP) in three children of two sisters were compared. The IQ of the child from an untreated pregnancy was 105; the developmental quotients of the two infant offspring from treated and untreated pregnancies were 122 and 114, respectively. The IQ of the sister with untreated MHP was 101; that of the sister who received dietary treatment for MHP during infancy was 90. Thus MHP and maternal MHP appear to have been clinically inconsequential in this family.

Phenylketonuria due to phenylalanine hydroxylase deficiency: an unfolding story. Medical Research Council Working Party on Phenylketonuria

Efficient neonatal screening for phenylketonuria and the availability of complex diets for lifelong use have virtually eliminated severe mental handicap from the disease. Nevertheless, there remains a high risk of fetal damage in offspring of women with the disease, and the possibility that the diets themselves may be harmful cannot be excluded. Search for a preventive treatment for the disease has been greatly aided by advances in molecular genetics. For example, in mice modified liver cells have been implanted, which have not only corrected the phenylalanine defect but have remained healthy for the normal life span of the animal. Overall, however, prevention and treatment have not progressed as quickly as was hoped, and research and development must be pursued vigorously to take account of contemporary perceptions of the disorder.

The use of gelatin capsules for ingestion of formula in dietary treatment of maternal phenylketonuria

Maternal phenylketonuria (PKU) represents a high risk for birth defects, including mental retardation, in offspring. Thus, it could cancel gains represented by the prevention of PKU-induced mental retardation in the current generation. Effective dietary treatment of maternal PKU pregnancies could avoid this potentially tragic occurrence. However, dietary compliance is often difficult because a necessary component of the diet, medical nutritional formulas, often have an unpleasant taste and odour. We treated the second pregnancy of a phenylketonuric women who had required extended hospitalization during her first pregnancy because of poor formula tolerance, and who had similar difficulty in the second pregnancy. To alleviate this problem, we developed a system whereby she could pack the formula into gelatin capsules for ingestion. Packing and ingestion of 20 capsules required less than 30 minutes three times a day. With capsules her blood phenylalanine level was almost always within the recommended range of 120-360 mumol/L (2-6 mg/dl) and hospitalization was not required. The phenylalanine content of the capsules was easily accommodated by a small reduction in allowable food. Other amino acid levels, including tyrosine and other essential nutrient levels, were normal. We believe that using gelatin capsules for formula ingestion can be very beneficial in the management of maternal PKU pregnancies and could be extended to the dietary treatment of other inborn errors of metabolism.

Late diagnosis of phenylketonuria in a Bedouin mother

We report on the first case of phenylketonuria in a Bedouin woman with 3 children having the phenylketonuria embryofetopathy. Herein, we discuss briefly hazards of late diagnosis of maternal phenylketonuria.