Blood Phenylalanine Concentrations Research Articles

Characteristics and outcomes of pregnancies among women with phenylketonuria from the NBS Connect registry

Women with phenylketonuria (PKU) should maintain blood phenylalanine (phe) concentration within the recommended range before and during pregnancy to prevent maternal PKU syndrome (MPKUS) in their offspring. Women who gave birth to children with MPKUS symptoms were more likely to report elevated phe concentration before pregnancy, and barriers to accessing components of their dietary management during pregnancy, including blood phe testing, medical food, modified low-protein foods, and healthcare visits with PKU specialists.

Phenylketonuria from the perspectives of patients in Türkiye

BackgroundThe present study aimed to determine the problems, unmet needs and expectations of phenylketonuria (PKU) patients in Türkiye regarding follow-up and treatment in order to provide data for future planning and implementations on PKU.MethodsThe study included patients diagnosed with PKU and/or their parents. They were informed about the study via phone calls and their verbal consents were obtained. Questions in the data collection forms, which were established separately for pediatric, adolescent, and adult age groups, were applied during the interviews and the answers were recorded.ResultsAmong 182 classical PKU patients, 66 (36.3%) were in the pediatric group (0–12 years old), 44 (24.2%) were in the adolescent group (13–19 years old), and 72 (39.5%) were in the adult group (≥ 20 years old). In all patient groups, phenylalanine-restricted diet and medical nutrition products were the main options for treatment. The median of the last measured blood phenylalanine concentration (patient-reported) was 290 µmol/L, 425 µmol/L, and 750 µmol/L in the pediatric, adolescent, and adult groups, respectively. The frequency of blood testing for serum phenylalanine level according to the age groups was appropriate in nearly half of the patients. While the majority of the patients have been visiting the metabolism center they have been diagnosed with PKU for control, considerable proportion of the patients would like to change the center or the doctor they visit for control if they could. It was determined that nearly half of the patients had trouble in accessing the metabolism center. Treatment options’ being limited and expensive were the major problems. The main requests of the patients and patient relatives included easier access to the metabolism centers and more options for treatment and diet.ConclusionsAccess to the services should be easier to improve the patients’ follow-up and treatment. There is need for low-cost, easily applicable, and accessible nutrition products and effective novel pharmacological agents. Focusing on these issues in health policies by providing pedagogic/psychological support, establishing support programs also comprising the families, and increasing the awareness activities were the key outcomes.

Analysis of gene variation and long-term follow-up in children with phenylalanine hydroxylase deficiency diagnosed by newborn screening.

To retrospectively analyze the variation and characteristics of phenylalanine hydroxylase (PAH) gene, and to observe the long-term treatment effect and follow-up of newborns with PAH deficiency. Clinical data, treatment and follow-up results of 198 patients with PAH deficiency diagnosed by newborn screening in Jinan from 1996 to 2021 were collected. The genetic analysis of 55 patients with PAH deficiency diagnosed by newborn screening in Jinan and 213 patients referred from the surrounding areas of Jinan were summarized. Gene variations were checked by a customized Panel gene detection method. Blood phenylalanine-concentration and physical development indicators including height and weight were regularly monitored. Intellectual development was assessed using a neuropsychological development scale for patients aged 0-6 years and academic performance, and brain injury in patients was assessed using brain magnetic resonance imaging. c.728G>A, c.158G>A, c.721C>T, c.1068C>A, c.611A>G variations were common in PAH gene. The genotype of c.158G>A variation is compound heterozygous variation, with mainly a mild hyperpheny-lalaninemia. 168 patients with PAH deficiency who were followed-up regularly had normal physical development without dwarfism or malnutrition. Among the 33 preschool patients who underwent mental development assessment, 2 were mentally retarded and the initial treatment age was older than 6 months. Nine patients with an average age of (17.13±2.42) years completed brain magnetic resonance imaging, one case was normal, and 8 cases were abnormal. There were patchy or patchy hyperintense foci near the bilateral lateral ventricles on T2WI, and the intellectual development was normal. Compared with the other eight patients, the blood phenylalanine concentration of the normal child was better and stably controlled within the ideal range. c.728G>A, c.158G>A, c.721C>T, c.1068C>A, c.611A>G variations were common in PAH gene. After standardized treatment, most patients with PAH deficiency diagnosed by screening can obtain normal growth and intellectual development in adolescence, but there are different degrees of organic lesions in the cerebral white matter.

In Silico Structural Protein Evaluation of the Phenylalanine Hydroxylase p.(Tyr77His) Variant Associated with Benign Hyperphenylalaninemia as Identified through Mexican Newborn Screening.

Hyperphenylalaninemia (HPA), which includes phenylketonuria (PKU), is a genetic autosomal recessive disorder arising from a deficiency in the enzyme named phenylalanine hydroxylase (PAH). Affected patients can experience severe and irreversible neurological impairments when phenylalanine (Phe) blood concentration exceeds 360 μmol/L (6 mg/dL). Here, we describe a female HPA patient who was born in Mexico to Cuban non-consanguineous parents and identified by newborn screening, and who bears the previously unreported PAH NM_000277.3(PAH):c.[229T>C];[1222C>T] or p.[Tyr77His];[Arg408Trp] genotype. At diagnosis, the patient showed a Phe blood level of 321 μmol/L (5.3 mg/dL), indicative of mild HPA. Neither of the PAH variants found in this patient had been previously reported in the mutational PAH spectrum of the Mexican population. The c.229T>C or p.(Tyr77His) PAH variant was previously related to mild HPA in the Swedish population. Our in silico structural analysis and molecular docking showed that mutated His 77 residue is located in the allosteric site of PAH at the interface of the two monomers. The PDBsum in silico tool predicted that this variant would cause minimal structural disturbance of the protein interface in the presence of Phe at the allosteric site. Docking studies revealed that these structural changes might be attenuated by the allosteric effect of Phe. Given the classic PKU phenotype conditioned by the "Celtic" or c.[1222C>T] or p.(Arg408Trp) PAH variant, which is the second variant in this patient, we propose that p.(Tyr77His) has a hypomorphic feature that could explain her mild HPA phenotype. Our results show the importance of following up on cases detected by NBS and the value of genetic studies and in silico tools that aid in the establishment of correct therapeutic strategies.

Complete correction of murine phenylketonuria by selection-enhanced hepatocyte transplantation.

Hepatocyte transplantation for genetic liver diseases has several potential advantages over gene therapy. However, the low efficiency of cell engraftment has limited its clinical implementation. This problem could be overcome by selectively expanding transplanted donor cells until they replace enough of the liver mass to achieve therapeutic benefit. We previously described a gene therapy method to selectively expand hepatocytes deficient in cytochrome p450 reductase (Cypor) using acetaminophen (APAP). Because Cypor is required for the transformation of APAP to a hepatotoxic metabolite, Cypor-deficient cells are protected from toxicity and are able to expand following APAP-induced liver injury. Here, we apply this selection system to correct a mouse model of phenylketonuria by cell transplantation. Hepatocytes from a wild-type donor animal were edited in vitro to create Cypor deficiency and then transplanted into phenylketonuric animals. Following selection with APAP, blood phenylalanine concentrations were fully normalized and remained stable following APAP withdrawal. Cypor-deficient hepatocytes expanded from < 1% to ~14% in corrected animals, and they showed no abnormalities in blood chemistries, liver histology, or drug metabolism. We conclude that APAP-mediated selection of transplanted hepatocytes is a potential therapeutic for phenylketonuria with long-term efficacy and a favorable safety profile.

Two-year interim safety and efficacy of pegvaliase in Japanese adults with phenylketonuria

Phenylketonuria (PKU) is an inborn error of metabolism caused by deficiency of phenylalanine hydroxylase, resulting in high blood phenylalanine (Phe) concentrations with potential for impaired neurocognition. Pegvaliase, a pegylated recombinant phenylalanine ammonia lyase that metabolizes Phe, is approved for use in adults with PKU and high blood Phe despite prior management. In the Phase 3 PRISM studies conducted in the United States, pegvaliase induction/titration/maintenance dosing led to clinically meaningful and statistically significant blood Phe reductions versus placebo, with a manageable safety profile. Here we report the primary endpoint, change in blood Phe levels from baseline to Week 52, and 2-year interim efficacy and safety results (to Week 144; data cut-off March 31, 2022) of an ongoing, open-label study in a Japanese PKU population (JapicCTI-194,642). Participants were 12 adults with PKU from Japan aged 18–70 years with blood Phe levels >600 μmol/L. In Part 1, participants received subcutaneous 2.5 mg pegvaliase once weekly for 4 weeks (induction), followed by titration up to 20 mg/day, then dose adjustment to a maximum 40 mg/day to achieve blood Phe efficacy (≤360 μmol/L); this maintenance dose was continued to Week 52. In Part 2, participants continued pegvaliase with dose adjustments up to a maximum 60 mg/day for up to 168 weeks. Among 11 participants evaluable for efficacy, mean (standard deviation) blood Phe concentration decreased from 1025.9 (172.7) μmol/L at baseline to 448.3 (458.8) μmol/L at Week 52 (mean 57.5% decrease). Up to Week 104, all 11 (100%) efficacy-evaluable participants achieved blood Phe levels ≤600 μmol/L, 9 (81.8%) achieved ≤360 μmol/L, and 8 (72.7%) achieved ≤120 μmol/L. All 12 participants reported ≥1 adverse event (AE), most commonly injection site erythema and injection site swelling (n = 10, 83.3% each). The pegvaliase exposure-adjusted AE rate was 23.5 per person-years overall, 41.2 per person-years during induction/titration, and 13.5 per person-years during maintenance. All participants developed pegvaliase-induced antibody responses. There were no AEs leading to discontinuation, no deaths, and no anaphylaxis events. Although interim, these results support the use of pegvaliase in Japanese adults with PKU with elevated blood Phe levels and are consistent with results from the Phase 3 PRISM studies.

Phenylalanine Tolerance over Time in Phenylketonuria: A Systematic Review and Meta-Analysis.

In phenylketonuria (PKU), natural protein tolerance is defined as the maximum natural protein intake maintaining a blood phenylalanine (Phe) concentration within a target therapeutic range. Tolerance is affected by several factors, and it may differ throughout a person's lifespan. Data on lifelong Phe/natural protein tolerance are limited and mostly reported in studies with low subject numbers. This systematic review aimed to investigate how Phe/natural protein tolerance changes from birth to adulthood in well-controlled patients with PKU on a Phe-restricted diet. Five electronic databases were searched for articles published until July 2020. From a total of 1334 results, 37 articles met the eligibility criteria (n = 2464 patients), and 18 were included in the meta-analysis. The mean Phe (mg/day) and natural protein (g/day) intake gradually increased from birth until 6 y (at the age of 6 months, the mean Phe intake was 267 mg/day, and natural protein intake was 5.4 g/day; at the age of 5 y, the mean Phe intake was 377 mg/day, and the natural protein intake was 8.9 g/day). However, an increase in Phe/natural protein tolerance was more apparent at the beginning of late childhood and was >1.5-fold that of the Phe tolerance in early childhood. During the pubertal growth spurt, the mean natural protein/Phe tolerance was approximately three times higher than in the first year of life, reaching a mean Phe intake of 709 mg/day and a mean natural protein intake of 18 g/day. Post adolescence, a pooled analysis could only be performed for natural protein intake. The mean natural protein tolerance reached its highest (32.4 g/day) point at the age of 17 y and remained consistent (31.6 g/day) in adulthood, but limited data were available. The results of the meta-analysis showed that Phe/natural protein tolerance (expressed as mg or g per day) increases with age, particularly at the beginning of puberty, and reaches its highest level at the end of adolescence. This needs to be interpreted with caution as limited data were available in adult patients. There was also a high degree of heterogeneity between studies due to differences in sample size, the severity of PKU, and target therapeutic levels for blood Phe control.

Blood phenylalanine fluctuation in phenylketonuric children treated by BH4 or low-phenylalanine diet from birth

The prognosis of phenylketonuria (PKU) is related to the quality of metabolic control all life-long. PKU treatment is based on a low-Phe diet, 6R-tetrahydrobiopterin (BH4) treatment for the BH4-responsive PKU patients or enzyme replacement therapy. Fluctuations in blood phenylalanine (Phe) concentrations may be an important determinant of intellectual outcome in patients with early and continuously treated phenylketonuria (PKU). The aim of this work is to study the fluctuation of Blood Phe in patients treated by BH4 from birth in comparison with patients treated by low-Phe diet. We conducted a retrospective study in a national reference center for PKU management. We compared mean phenylalanine blood concentration and its fluctuation in 10 BH4-responder patients (BH4R) and in 10 BH4 non-responder patients (BH4NR) treated from birth. The mean blood Phe concentration is similar between the two groups before 10 years of age (290 ± 135 (BH4R) vs. 329 ± 187 µmol/L, p = 0.066 (BH4NR)) while it is lower in the BH4R group after 10 years of age. (209 ± 69 vs. 579 ± 136 µmol/L, p = 0.0008). Blood Phe fluctuation is significantly lower in the BH4R group compared to the BH4NR group (70.2 ± 75.6 vs. 104.4 ± 111.6 µmol/L, p < 0.01) before 6 years of age. There are no significant differences observed on nutritional status, growth, and neuropsychological tests between the two groups. BH4 introduced in the neonatal period is associated with less blood Phe fluctuation before 6 years. Additional time and patients are required to determine if the decrease in Phe fluctuation would positively impact the long-term outcome of PKU patients.

Two years of pegvaliase in Germany: Experiences and best practice recommendations.

In 2019, pegvaliase was approved in Europe for the treatment of phenylketonuria (PKU) in patients aged 16years and older with blood phenylalanine (Phe) concentrations above 600μmol/L despite prior management with available treatment options. Since its European approval, German metabolic centres have gained valuable experience, which may be of benefit to other treatment centres managing patients on pegvaliase. After a virtual meeting that was attended by nine German physicians, three German dietitians and one American physician, a follow-up discussion was held via an online platform to develop a set of recommendations on the use of pegvaliase in Germany. Eight German physicians contributed to the follow-up discussion and subsequent consensus voting, using a modified Delphi technique. The recommendations were supported by literature and retrospectively collected patient data. Consensus (≥75% agreement) was achieved on 25 recommendations, covering seven topics deemed relevant by the expert panel when considering pegvaliase an option for the treatment of patients with PKU. In addition to the recommendations, a retrospective chart review was conducted in seven of the centres and included 71 patients who initiated treatment with pegvaliase. Twenty-seven patients had been treated for at least 24months and 23 (85.2%) had achieved blood Phe ≤600μmol/L with some degree of diet normalisation. Of these patients, 14 had physiological blood Phe on a normalised diet. The practical consensus recommendations provide guidance on the different steps along the pegvaliase journey from clinical site requirements to treatment goals and outcomes. The recommendations are intended to support less experienced European metabolic centres with the implementation of pegvaliase, emphasising that a core treatment team consisting of at least a dietitian and metabolic physician is sufficient to initiate pegvaliase and support patients during their treatment journey.

Competitive, multi-objective, and compartmented Flux Balance Analysis for addressing tissue-specific inborn errors of metabolism.

The inborn error of metabolism phenylketonuria (PKU, OMIM 261600) is most often due to inactivation of phenylalanine hydroxylase (PAH), which converts phenylalanine (Phe) into tyrosine (Tyr). The reduced PAH activity increases blood concentration of phenylalanine and urine levels of phenylpyruvate. Flux balance analysis (FBA) of a single-compartment model of PKU predicts that maximum growth rate should be reduced unless Tyr is supplemented. However, the PKU phenotype is lack of development of brain function specifically, and Phe reduction rather than Tyr supplementation cures the disease. Phe and Tyr cross the blood-brain barrier (BBB) through the aromatic amino acid transporter implying that the two transport reactions interact. However, FBA does not accommodate such competitive interactions. We here report on an extension to FBA that enables it to deal with such interactions. We built a three-compartment model, made the common transport across the BBB explicit, and included dopamine and serotonin synthesis as parts of the brain function to be delivered by FBA. With these ramifications, FBA of the genome-scale metabolic model extended to three compartments does explain that (i) the disease is brain specific, (ii) phenylpyruvate in urine is a biomarker, (iii) excess of blood-phenylalanine rather than shortage of blood-tyrosine causes brain pathology, and (iv) Phe deprivation is the better therapy. The new approach also suggests (v) explanations for differences in pathology between individuals with the same PAH inactivation, and (vi) interference of disease and therapy with the functioning of other neurotransmitters.

Myelin basic protein recovery during PKU mice lifespan and the potential role of microRNAs on its regulation

Untreated phenylketonuria (PKU) patients and PKU animal models show hypomyelination in the central nervous system and white matter damages, which are accompanied by myelin basic protein (MBP) impairment. Despite many assumptions, the primary explanation of the mentioned cerebral outcomes remains elusive. In this study, MBP protein and mRNA expression on brains of wild type (WT) and phenylketonuric (ENU2) mice were analyzed throughout mice lifespan (14-60-180-270-360-540 post-natal days, PND). The results confirmed the low MBP expression at first PND times, while revealed an unprecedented progressive MBP protein expression recovery in aged ENU2 mice. Unexpectedly, unaltered MBP mRNA expression between WT and ENU2 was always observed. Additionally, for the same time intervals, a significant decrease of the phenylalanine concentration in the peripheral blood and brain of ENU2 mice was detected, to date, for the first time. In this scenario, a translational hindrance of MBP during initial and late cerebral development in ENU2 mice was hypothesized, leading to the execution of a microRNA microarray analysis on 60 PND brains, which was followed by a proteomic assay on 60 and 360 PND brains in order to validate in silico miRNA-target predictions. Taken together, miR-218-1-3p, miR-1231-3p and miR-217-5p were considered as the most impactful microRNAs, since a downregulation of their potential targets (MAG, CNTNAP2 and ANLN, respectively) can indirectly lead to a low MBP protein expression. These miRNAs, in addition, follow an opposite expression trend compared to MBP during adulthood, and their target proteins revealed a complete normalization in aged ENU2 mice. In conclusion, these results provide a new perspective on the PKU pathophysiology understanding and on a possible treatment, emphasizing the potential modulating role of differentially expressed microRNAs in MBP expression on PKU brains during PKU mouse lifespan.

Pegvaliase (Palynziq)

&#x0D; CADTH reimbursement reviews are comprehensive assessments of the clinical effectiveness and cost-effectiveness, as well as patient and clinician perspectives, of a drug or drug class.&#x0D; The assessments inform non-binding recommendations that help guide the reimbursement decisions of Canada's federal, provincial, and territorial governments, with the exception of Quebec.&#x0D; This review assesses Pegvaliase (Palynziq), pre-filled syringes: 2.5 mg/0.5 mL (5 mg/mL), 10 mg/0.5 mL (20 mg/mL), 20 mg/mL, solution for subcutaneous injection.&#x0D; Indication: Palynziq (pegvaliase injection) is indicated to reduce blood phenylalanine concentrations in patients with phenylketonuria aged 16 years and older who have inadequate blood phenylalanine control (blood phenylalanine levels greater than 600 µmol/L) despite dietary management.&#x0D;

Phenylalanine free infant formula in the dietary management of phenylketonuria

BackgroundPhenylalanine-free infant formula is an essential source of safe protein in a phenylalanine restricted diet, but its efficacy is rarely studied. We report a multicentre, open, longitudinal, prospective intervention study on a phenylalanine-free infant formula (PKU Start: Vitaflo International Ltd.).ResultsThis was a 2-part study: part I (28 days short term evaluation) and part II (12 months extension). Data was collected on infant blood phenylalanine concentrations, dietary intake, growth, and gastrointestinal tolerance. Ten infants (n = 8 males, 80%), with a median age of 14 weeks (range 4–36 weeks) were recruited from 3 treatment centres in the UK. Nine of ten infants completed the 28-day follow-up (one caregiver preferred the usual phenylalanine-free formula and discontinued the study formula after day 14) and 7/9 participated in study part II. The phenylalanine-free infant formula contributed a median of 57% (IQR 50–62%) energy and 53% (IQR 33–66%) of total protein intake from baseline to the end of the part II extension study. During the 12-month follow-up, infants maintained normal growth and satisfactory blood phenylalanine control. Any early gastrointestinal symptoms (constipation, colic, vomiting and poor feeding) improved with time.ConclusionThe study formula was well tolerated, helped maintain good metabolic control, and normal growth in infants with PKU. The long-term efficacy of phenylalanine-free infant formula should continue to be observed and monitored.

Protein substitutions as new-generation pharmanutrition approach to managing phenylketonuria.

Phenylketonuria (PKU), an autosomal recessive inherited metabolic disorder, is caused by a mutation in the phenylalanine hydroxylase (PAH) gene on the 12th chromosome. Defective PAH activity ultimately leads to increased phenylalanine (Phe) blood concentrations (hyperphenylalaninemia) that harm the brain. The primary purpose of PKU treatment is to maintain the blood Phe level to prevent certain undesired effects. Hence, lifelong medical nutrition therapy is recommended for these patients. The usefulness of natural protein sources may be limited, as they are based on individual Phe tolerance, and a patient's daily protein requirements are supported by Phe-free amino acid mixtures. A few PKU treatment centers recently started using supplemental casein glycomacropeptide, pegvaliase, or large neutral amino acids, and some patients are treated by responding to tetrahydrobiopterin, which works as a pharmaceutical chaperone (prescribed as sapropterin dihydrochloride). This review discusses the efficacy and safety considerations of basic medical nutrition approaches and newgeneration protein substitutes that are used to treat PKU.

The Impact of the Quality of Nutrition and Lifestyle in the Reproductive Years of Women with PKU on the Long-Term Health of Their Children.

A woman’s nutritional status before and during pregnancy can affect the health of her progeny. Phenylketonuria (PKU), a rare disorder causing high blood and brain phenylalanine (Phe) concentrations, is associated with neurocognitive disability. Lifelong treatment is mainly dietetic with a Phe-restricted diet, supplemented with a low-Phe protein substitute. Treatment adherence commonly decreases in adolescence, with some adults ceasing dietary treatment. In maternal PKU, elevated blood Phe is harmful to the fetus so a strict Phe-restricted diet must be re-established preconception, and this is particularly difficult to achieve. A woman’s reproductive years introduces an opportunity to adopt healthier behaviours to prepare for successful pregnancies and positive health outcomes for both themselves and their children. Several factors can influence the health status of women with PKU. Political, socioeconomic, and individual food and lifestyle choices affect diet quality, metabolic control, and epigenetics, which then pre-condition the overall maternal health and long-term health of the child. Here, we reflect on a comprehensive approach to treatment and introduce practical recommendations to optimize the wellbeing of women with PKU and the resultant health of their children.

Management precautions for risk of obesity are necessary among infants with PKU carrying the rs113883650 variant of the LAT1 gene: A cross-sectional study

Patients with phenylketonuria (PKU), an inborn error of phenylalanine metabolism, require consistent treatment to avoid the brain toxicity caused by hyperphenylalaninemia. The treatment consists of life-long use of a low-phenylalanine diet, which aims at decreasing hyperphenylalaninemia and maintaining blood phenylalanine concentration in a safe range. Problems with balancing diet can result in suboptimal treatment outcomes; however, recent findings suggest that genetic alteration of the transport of phenylalanine might result in an additional health burden. We assessed the effect of a common variant (rs113883650) of the LAT1(SLC7A5) gene, which encodes the main transmembrane phenylalanine transporter, on the development of overweight in 54 infants with PKU who received standard therapy and adhered well to therapeutic prescriptions, and in 55 infants with a milder disease form—the so-called mild hyperphenylalaninemia (MHP), which does not require treatment. We found that infants with PKU—carriers of the rs113883650 variant had significantly higher Body Mass Index (BMI) at 1 year compared to PKU infants without the variant (mean BMI Z-Score of +1.15 SD vs -0.15 SD, respectively; t(52) = 5.25, p = 0.00005). Conversely, no significant BMI differences were detected in the subgroups of infants with MHP (t(53) = 1.15, p = 0.25). Additionally, high BMI in infants with PKU—carriers of the rs113883650 variant positively correlated with high variability of their blood phenylalanine levels (r(52) = 0.42, p = 0.002). It should be noted that this is an observational study, which does not determine causation. Nevertheless, our findings show that the rs113883650 variant of the LAT1 gene may be a risk factor for overweight in properly treated infants with PKU. Management precautions should be taken to prevent the development of overweight and obesity.

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.

Telehealth and COVID-19: Empowering Standards of Management for Patients Affected by Phenylketonuria and Hyperphenylalaninemia.

Phenylketonuria (PKU) and Hyperphenylalaninemia (HPA) are inborn errors of metabolism (IEM) due to mutations in the PAH gene resulting in increased blood phenylalanine (Phe) concentrations. Depending on the Phe levels, a lifelong dietary intervention may be needed. During the COVID-19 pandemic, finding new strategies to ensure follow-up and metabolic control for such patients became mandatory and telehealth was identified as the most eligible tool to provide care and assistance beyond barriers. The aim of this study was to evaluate how telehealth use may have impacted disease follow-ups. Seven hundred and fifty-five patients affected by PKU/HPA in follow-ups at the Clinical Department of Pediatrics (San Paolo Hospital, ASST Santi Paolo e Carlo, University of Milan, Italy) were included in this study. The data regarding the used telehealth model, type of performed consultations and patients’ perspectives were retrospectively collected and analyzed after a one-year experience of implemented follow-ups. The results demonstrated that telehealth seemed to be a useful tool to improve the adherence to treatment and that it could guarantee continuous assistance and care beyond the surrounding epidemiological status. Patients expressed great satisfaction with the offered services and requested that they were implemented in standards of care on a long-term basis. Our results suggested the implementation of telehealth in the management guidelines for PKU/HPA patients.

Natural history of children and adults with phenylketonuria in the NBS-PKU Connect registry

PurposePhenylalanine hydroxylase deficiency, or phenylketonuria (PKU), is a rare autosomal recessive metabolic disorder. Early diagnosis via newborn screening (NBS) and initiation of treatment prevent the development of cognitive impairment and other co-morbidities. The purpose of this study is to describe the natural history of PKU in the United States, including prevalence of co-morbidities and predictors of outcomes. MethodsWe analyzed data from a self-report survey in the NBS-PKU Connect online registry. We describe the participants' nutrition management strategies, barriers to management, outcomes of bone disorders, skin, and psychological co-morbidities, and the use of special education or other special services. Predictors of outcomes were identified and assessed, including the impact of sex, age, age at diagnosis, blood phenylalanine concentration, use of sapropterin, use of medical food, adherence to prescribed diet, use of low protein modified foods, whether they had ever been off-diet, and use of tyrosine supplementation. ResultsThe 219 respondents included individuals with PKU or hyperphenylalanemia (n = 78), or their caregivers (n = 141). Most (84.3%) started treatment before the age of two weeks. About one-third indicated that they had been off-diet at some point in their lives, and 81.4% reported that they currently adhered to their prescribed diet, with adherence to prescribed diet decreasing with age. Blood phenylalanine concentration was under the recommended threshold of 360 μmol/L for 68.5% of participants. One-quarter of respondents reported psychological co-morbidities, with anxiety and ADD/ADHD being the most common. The incidence of psychological co-morbidities increased with age and with ever having been off diet. Special education or other special services were more likely to be reported by individuals who were diagnosed after one week of age. Skin disorders such as acne and eczema were more common in females than males, and a minority of participants reported bone disorders. ConclusionsDespite recommendations to maintain blood phenylalanine concentrations in the therapeutic range throughout life, it is not uncommon for adults with PKU to discontinue dietary management of their disorder. Early diagnosis was associated with reduced need for special education or other special services, and continuous treatment was associated with decreased psychological co-morbidities.

Long-term cognitive and psychosocial outcomes in adults with phenylketonuria.

Previous studies have suggested that cognitive and psychosocial underfunctioning in early-treated adults with phenylketonuria (PKU) may be explained by suboptimal adherence to dietary treatments, however, these studies often employ small samples, with different outcome measures, definitions and cut-offs. Samples have also tended to comprise participants with a limited range of blood phenylalanine concentrations, and often individuals who may not have been treated early enough to avoid neurological damage. In this study, we explore the impact of lifetime dietary control, as indicated by blood phenylalanine concentrations in childhood, adolescence and adulthood, on long-term cognitive and psychosocial outcomes in a large sample of adults with PKU who were diagnosed by neonatal screening and commenced on dietary treatment within the first month of life. One hundred and fifty-four participants underwent cognitive testing, assessing attention, learning, working memory, language, executive functioning and processing speed. One hundred and forty-nine completed measures of psychosocial functioning, documenting educational, occupational, quality of life, emotional and social outcomes which were compared with a group of healthy controls. Many adults with PKU demonstrated cognitive impairments, most frequently affecting processing speed (23%), executive function (20%) and learning (12%). Cognitive outcomes were related to measures of historic metabolic control, but only processing speed was significantly related to phenylalanine concentration at the time of testing after controlling for historic levels. Adults with PKU did not, however, differ from controls in educational, occupational, quality of life or emotional outcomes, or on a measure of family functioning, and showed only minor differences in relationship style. These findings have implications for patient counselling and decisions regarding the management of PKU in adulthood.