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

Preventing maternal phenylketonuria (PKU) syndrome: important factors to achieve good metabolic control throughout pregnancy

Background

Insufficient metabolic control during pregnancy of mothers with phenylketonuria (PKU) leads to maternal PKU syndrome, a severe embryo-/fetopathy. Since maintaining or reintroducing the strict phenylalanine (Phe) limited diet in adults with PKU is challenging, we evaluated the most important dietary and psychosocial factors to gain and sustain good metabolic control in phenylketonuric women throughout pregnancy by a questionnaire survey with 38 questions concerning therapy feasibility. Among them, the key questions covered 5 essential items of PKU care as follows: General information about maternal PKU, PKU training, diet implementation, individual metabolic care, personal support. In addition, all participating PKU mothers were asked to estimate the quality of their personal metabolic control of the concluded pregnancies. 54 PKU mothers with 81 pregnancies were approached at 12 metabolic centers in Germany and Austria were included. According to metabolic control, pregnancies of PKU women were divided in two groups: group “ideal” (not more than 5% of all blood Phe concentrations during pregnancy > 360 µmol/l; n = 23) and group “suboptimal” (all others; n = 51).

Results

The demand for support was equally distributed among groups, concerning both amount and content. Personal support by the direct social environment (partner, family and friends) (“suboptimal” 71% vs “ideal” 78%) as well as individual metabolic care by the specialized metabolic center (both groups around 60%) were rated as most important factors. The groups differed significantly with respect to the estimation of the quality of their metabolic situation (p < 0.001). Group “ideal” presented a 100% realistic self-assessment. In contrast, group “suboptimal” overestimated their metabolic control in 53% of the pregnancies. Offspring of group “suboptimal” showed clinical signs of maternal PKU-syndrome in 27%.

Conclusion

The development of training programs by specialized metabolic centers for females with PKU in child bearing age is crucial, especially since those mothers at risk of giving birth to a child with maternal PKU syndrome are not aware of their suboptimal metabolic control. Such programs should provide specific awareness training for the own metabolic situation and should include partners and families.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02108-5.

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.

Low increase in phenylalanine tolerance during pregnancies in PKU woman with high prepregnancy BMI and postconceptional initiation of diet: A case report

Background

Women with untreated phenylketonuria (PKU) are at an increased risk to have offspring with multiple abnormalities due to teratogenic effects of hyperphenylalaninaemia. Treatment goals include blood phenylalanine concentrations between 120 and 360 µmol/L, however, there are limited pieces of evidence for the practical management of pregnant PKU patient and prediction of phenylalanine tolerance changes during a course of pregnancy.

Case

We report the case of a mother with classical PKU (p.R408W/p.R408W) and the course of her two pregnancies with low phenylalanine tolerance increase (347mg and 227mg) despite the rewarding collaboration with a nutritionist.

Conclusion

This case report does not confirm the observation that a very low phenylalanine tolerance increase in pregnancy of PKU patient is a marker of coexisting PKU-affection in fetus.

Ten years of specialized adult care for phenylketonuria - a single-centre experience

Background

Specialized adult care of phenylketonuria (PKU) patients is of increasing importance. Adult outpatient clinics for inherited errors of metabolism can help to achieve this task, but experience is limited. Ten years after establishment of a coordinated transition process and specialised adult care for inherited metabolic diseases, adult PKU care was evaluated with respect to metabolic control, therapy satisfaction, life satisfaction, sociodemographic data, economical welfare as well as pregnancy outcome.

Methods

All PKU patients transferred from paediatric to adult care between 2005 and 2015 were identified. A retrospective data analysis and a cross-sectional survey in a sub-cohort of 30 patients including a questionnaire for assessing quality of life (FLZm) were performed as a single-centre investigation at the metabolic department of the University Hospital Leipzig, Germany. For statistical analysis, Mann-Whitney-U-test, t-test for independent samples, ANOVA and chi square test were used as appropriate.

Results

96 PKU patients (56 females/40 males; median age 32 years, range 18–62) were included. In the last 3-year period, 81 % of the transferred patients still kept contact to the adult care centre. Metabolic control was stable over the evaluation period and dried blood phenylalanine concentrations mostly remained within the therapeutic range (median 673.0 μmol/l, range 213.0–1381.1). Sociodemographic data, economical welfare and life satisfaction data were comparable to data from the general population. However, differences could be revealed when splitting the cohort according to time of diagnosis and to management during childhood. 83 % of the PKU adults were satisfied with the transition process and current adult care. 25 completed pregnancies were supervised; three newborns, born after unplanned pregnancy, showed characteristic symptoms of maternal PKU syndrome.

Conclusions

Continuous care for adult PKU patients in a specialized outpatient clinic is successful, leading to good to satisfactory metabolic control and social outcomes. Uninterrupted good metabolic treatment throughout childhood and adolescence positively influences educational, professional and economic success in later life. Further effort in specialized paediatric and adult metabolic care is needed to prevent loss of follow-up and to support the recommended life-long treatment and/or care.

Showing Value in Newborn Screening: Challenges in Quantifying the Effectiveness and Cost-Effectiveness of Early Detection of Phenylketonuria and Cystic Fibrosis

Decision makers sometimes request information on the cost savings, cost-effectiveness, or cost-benefit of public health programs. In practice, quantifying the health and economic benefits of population-level screening programs such as newborn screening (NBS) is challenging. It requires that one specify the frequencies of health outcomes and events, such as hospitalizations, for a cohort of children with a given condition under two different scenarios-with or without NBS. Such analyses also assume that everything else, including treatments, is the same between groups. Lack of comparable data for representative screened and unscreened cohorts that are exposed to the same treatments following diagnosis can result in either under- or over-statement of differences. Accordingly, the benefits of early detection may be understated or overstated. This paper illustrates these common problems through a review of past economic evaluations of screening for two historically significant conditions, phenylketonuria and cystic fibrosis. In both examples qualitative judgments about the value of prompt identification and early treatment to an affected child were more influential than specific numerical estimates of lives or costs saved.

Breastfeeding infants with phenylketonuria in the United States and Canada

OBJECTIVE

This study described the prevalence and duration of mothers' breastfeeding infants with phenylketonuria (PKU) and explored factors related to duration of breastfeeding as a surrogate for breastfeeding success.

SUBJECTS AND METHODS

Descriptive analysis as performed from an international Internet survey of mothers (n=103) who met the inclusion criteria: (1) at least 21 years of age, (2) able to read and write in English, (3) child with PKU, and (4) living in the United States or Canada.

RESULTS

Of the 103 mothers, 89 (86%) initiated breastfeeding immediately following delivery, whereas 14 (14%) chose bottle feeding. In comparison to breastfeeding after delivery, significantly fewer mothers breastfed after diagnosis (McNemar's χ(2)=30.33, p<0.001; n=72 vs. n=89). Breastfeeding duration ranged from less than 1 month to 24 months with one modal duration category (n=20, 22%) at less than 1 month. The timing of the addition of commercial infant formula to supplement breastfeeding or expressed mothers' milk was associated with a shorter duration of breastfeeding among infants with PKU: χ(2) (42, n=73)=88.13, p<0.001.

CONCLUSIONS

PKU is treated with phenylalanine (Phe) restriction. Breastfeeding infants with PKU is challenging in part because Phe intake is difficult to determine precisely. We studied breastfeeding duration in infants with PKU and factors associated with success. Further research should identify the unique needs of mothers' breastfeeding infants with PKU to guide the development of interventions specific to these mothers to support their efforts to continue breastfeeding after the diagnosis of PKU.

Association of common variants in PAH and LAT1 with non-syndromic cleft lip with or without cleft palate (NSCL/P) in the Polish population

BACKGROUND

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is a common structural malformation with a complex and multifactorial aetiology. Associations of abnormalities in phenylalanine metabolism and orofacial clefts have been suggested.

METHODS

Eight single nucleotide polymorphisms (SNPs) of genes encoding phenylalanine hydroxylase (PAH) and large neutral l-amino acid transporter type 1 (LAT1), as well as the PAH mutation that is most common in the Polish population (rs5030858; R408W), were investigated in 263 patients with NSCL/P and 270 matched controls using high resolution melting curve analysis (HRM).

RESULTS

We found that two polymorphic variants of PAH appear to be risk factors for NSCL/P. The odds ratio (OR) for individuals with the rs7485331 A allele (AC or AA) compared to CC homozygotes was 0.616 (95% confidence interval [CI]=0.437-0.868; p=0.005) and this association remains statistically significant after multiple testing correction. The PAH rs12425434, previously associated with schizophrenia, was borderline associated with orofacial clefts. Moreover, haplotype analysis of polymorphisms in the PAH gene revealed a 4-marker combination that was significantly associated with NSCL/P. The global p-value for a haplotype comprised of SNPs rs74385331, rs12425434, rs1722392, and the mutation rs5030858 was 0.032, but this association did not survive multiple testing correction.

CONCLUSION

This study suggests the involvement of the PAH gene in the aetiology of NSCL/P in the tested population. Further replication will be required in separate cohorts to confirm the consistency of the observed association.

Cardiac teratogenicity in mouse maternal phenylketonuria: defining phenotype parameters and genetic background influences

Maternal phenylketonuria (MPKU) is a syndrome including cardiovascular malformations (CVMs), microcephaly, intellectual impairment, and small size for gestational age, caused by in-utero exposure to elevated serum phenylalanine (Phe) due to PKU in the mother. It is becoming a public health concern as more women with PKU reach child bearing age. Although a mouse model of PKU, BTBR Pah(enu2), has been available for 20 years, it has not been well utilized for studying MPKU. We used this model to delineate critical parameters in Phe cardiovascular teratogenicity and study the effect of genetic background. Dosing and timing experiments were performed with the BTBR Pah(enu2) mouse. A dose response curve was noted, with CVM rates at maternal serum Phe levels <360 μM (control), 360-600 μM (low), 600-900 μM (mid), and >900 μM (high) of 11.86%, 16.67%, 30.86%, and 46.67% respectively. A variety of CVMs were noted on the BTBR background, including double outlet right ventricle (DORV), aortic arch artery (AAA) abnormalities, and ventricular septal defects (VSDs). Timed exposure experiments identified a teratogenic window from embryonic day 8.5-13.5, with higher rates of conotruncal and valve defects occurring in early exposure time and persistent truncus arteriosus (PTA) and aortic arch branching abnormalities occurring with late exposure. Compared to the BTBR strain, N10+ Pah(enu2) congenics on the C3H/HeJ background had higher rates of CVMs in general and propensity to left ventricular outflow tract (LVOT) malformations, while the C57B/L6 background had similar CVM rates but predominately AAA abnormalities. We have delineated key parameters of Phe cardiovascular teratogenicity, demonstrated the utility of this MPKU model on different mouse strains, and shown how genetic background profoundly affects the phenotype.