Metabolic control during the neonatal period in phenylketonuria: associations with childhood IQ

Insurance Reimbursement for Special Foods and Phenylalanine Levels in Patients With PKU in China

Importance

Recent changes in China's social medical insurance reimbursement policy have impacted the financial burden of patients with phenylketonuria (PKU) for special foods. However, whether this policy change is associated with their blood phenylalanine (PHE) concentration is unclear.

Objective

To investigate the association between the reimbursement policy and blood PHE concentration in patients with PKU.

Design, Setting, and Participants

This cohort study measured the blood PHE concentrations of 167 patients with PKU across 4 newborn screening centers in China from January 2018 to December 2021. The reimbursement policy for special foods for patients with PKU at 2 centers was canceled in 2019 and restored from 2020 onwards. In contrast, the other 2 centers consistently implemented the policy. Data were analyzed from September 10 to December 6, 2023.

Exposures

The implementation and cancelation of the reimbursement policy for special foods of patients with PKU.

Main Outcomes and Measures

The blood PHE concentration was regularly measured from 2018 to 2021. A 1-sided Z test was used to compare the mean of the blood PHE concentration between different years.

Results

Among 167 patients with PKU (mean [SD] age, 84.4 [48.3] months; 87 males [52.1%]), a total of 4285 measurements of their blood PHE concentration were collected from 2018 to 2021. For patients at the center that canceled the reimbursement policy in 2019, the mean (SD) of the blood PHE concentrations in 2019 was 5.95 (5.73) mg/dL, significantly higher than 4.84 (4.11) mg/dL in 2018 (P < .001), 5.06 (5.21) mg/dL in 2020 (P = .006), and 4.77 (4.04) mg/dL in 2021 (P < .001). Similarly, for patients at the other center that canceled the policy in 2019, the mean (SD) of the blood PHE concentrations in 2019 was 5.95 (3.43) mg/dL, significantly higher than 5.34 (3.45) mg/dL in 2018 (P = .03), 5.13 (3.15) mg/dL in 2020 (P = .003), and 5.39 (3.46) mg/dL in 2021 (P = .03). On the contrary, no significant difference was observed between any of the years for patients at the 2 centers that consistently implemented the policy.

Conclusions and Relevance

In this cohort study of patients with PKU from multiple centers, the implementation of the reimbursement policy for special foods was associated with controlling the blood PHE concentration. Special foods expenditure for patients with PKU should be included in the scope of long-term social medical insurance reimbursement.

Phenylalanine hydroxylase deficiency treatment and management: A systematic evidence review of the American College of Medical Genetics and Genomics (ACMG)

PURPOSE

Elevated serum phenylalanine (Phe) levels due to biallelic pathogenic variants in phenylalanine hydroxylase (PAH) may cause neurodevelopmental disorders or birth defects from maternal phenylketonuria. New Phe reduction treatments have been approved in the last decade, but uncertainty on the optimal lifespan goal Phe levels for patients with PAH deficiency remains.

METHODS

We searched Medline and Embase for evidence of treatment concerning PAH deficiency up to September 28, 2021. Risk of bias was evaluated based on study design. Random-effects meta-analyses were performed to compare IQ, gestational outcomes, and offspring outcomes based on Phe ≤ 360 μmol/L vs > 360 μmol/L and reported as odds ratio and 95% CI. Remaining results were narratively synthesized.

RESULTS

A total of 350 studies were included. Risk of bias was moderate. Lower Phe was consistently associated with better outcomes. Achieving Phe ≤ 360 μmol/L before conception substantially lowered the risk of negative effect to offspring in pregnant individuals (odds ratio = 0.07, 95% CI = 0.04-0.14; P < .0001). Adverse events due to pharmacologic treatment were common, but medication reduced Phe levels, enabling dietary liberalization.

CONCLUSIONS

Reduction of Phe levels to ≤360 μmol/L through diet or medication represents effective interventions to treat PAH deficiency.

Communication of an Abnormal Metabolic New-Born Screening Result in The Netherlands: The Parental Perspective

In the Netherlands, abnormal New-Born Screening (NBS) results are communicated to parents by the general practitioner (GP). Good communication and consequential trust in professionals is of the utmost importance in the treatment of phenylketonuria (PKU). The aim of this study was to assess parental satisfaction regarding the communication of an abnormal NBS result for PKU in the Netherlands. An email containing the link to a web-based questionnaire was sent by the Dutch PKU Association to their members. Responses to open questions were categorized, data of both open and closed questions were analysed with descriptive statistics and the Chi-Square test using SPSS. Out of 113 parents of a child with PKU (born between 1979 and 2020), 68 stated they were overall unsatisfied with the first communication of the NBS result. Seventy-five parents indicated that wrong or no information about PKU was given. A significant decrease was found in the number of parents being contact by their own GP over the course of 40 years (p < 0.05). More than half of all parents were overall unsatisfied with the first communication of the abnormal NBS result for PKU. Further research on how to optimize communication of an abnormal NBS results is necessary.

Genetic etiology and clinical challenges of phenylketonuria

This review discusses the epidemiology, pathophysiology, genetic etiology, and management of phenylketonuria (PKU). PKU, an autosomal recessive disease, is an inborn error of phenylalanine (Phe) metabolism caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene. The prevalence of PKU varies widely among ethnicities and geographic regions, affecting approximately 1 in 24,000 individuals worldwide. Deficiency in the PAH enzyme or, in rare cases, the cofactor tetrahydrobiopterin results in high blood Phe concentrations, causing brain dysfunction. Untreated PKU, also known as PAH deficiency, results in severe and irreversible intellectual disability, epilepsy, behavioral disorders, and clinical features such as acquired microcephaly, seizures, psychological signs, and generalized hypopigmentation of skin (including hair and eyes). Severe phenotypes are classic PKU, and less severe forms of PAH deficiency are moderate PKU, mild PKU, mild hyperphenylalaninaemia (HPA), or benign HPA. Early diagnosis and intervention must start shortly after birth to prevent major cognitive and neurological effects. Dietary treatment, including natural protein restriction and Phe-free supplements, must be used to maintain blood Phe concentrations of 120-360 μmol/L throughout the life span. Additional treatments include the casein glycomacropeptide (GMP), which contains very limited aromatic amino acids and may improve immunological function, and large neutral amino acid (LNAA) supplementation to prevent plasma Phe transport into the brain. The synthetic BH4 analog, sapropterin hydrochloride (i.e., Kuvan®, BioMarin), is another potential treatment that activates residual PAH, thus decreasing Phe concentrations in the blood of PKU patients. Moreover, daily subcutaneous injection of pegylated Phe ammonia-lyase (i.e., pegvaliase; PALYNZIQ®, BioMarin) has promised gene therapy in recent clinical trials, and mRNA approaches are also being studied.

Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier

Phenylketonuria (PKU) is an inborn error of metabolism caused by variants in the phenylalanine hydroxylase (PAH) gene and it is characterized by excessively high levels of phenylalanine in body fluids. PKU is a paradigm for a genetic disease that can be treated and majority of developed countries have a population-based newborn screening. Thus, the combination of early diagnosis and immediate initiation of treatment has resulted in normal intelligence for treated PKU patients. Although PKU is a monogenic disease, decades of research and clinical practice have shown that the correlation between the genotype and corresponding phenotype is not simple at all. Attempts have been made to discover modifier genes for PKU cognitive phenotype but without any success so far.

We conducted whole genome sequencing of 4 subjects from unrelated non-consanguineous families who presented with pathogenic mutations in the PAH gene, high blood phenylalanine concentrations and near-normal cognitive development despite no treatment. We used cross sample analysis to select genes common for more than one patient. Thus, the SHANK gene family emerged as the only relevant gene family with variants detected in 3 of 4 analyzed patients. We detected two novel variants, p.Pro1591Ala in SHANK1 and p.Asp18Asn in SHANK2, as well as SHANK2:p.Gly46Ser, SHANK2:p.Pro1388_Phe1389insLeuPro and SHANK3:p.Pro1716Thr variants that were previously described. Computational analysis indicated that the identified variants do not abolish the function of SHANK proteins. However, changes in posttranslational modifications of SHANK proteins could influence functioning of the glutamatergic synapses, cytoskeleton regulation and contribute to maintaining optimal synaptic density and number of dendritic spines.

Our findings are linking SHANK gene family and brain plasticity in PKU for the first time. We hypothesize that variant SHANK proteins maintain optimal synaptic density and number of dendritic spines under high concentrations of phenylalanine and could have protective modifying effect on cognitive development of PKU patients.