The efficacy of Carbamylglutamate impacts the nutritional management of patients with N-Acetylglutamate synthase deficiency.

BACKGROUND: The autosomal recessive disorder N-acetylglutamate synthase (NAGS) deficiency is the rarest defect of the urea cycle, with an incidence of less than one in 2,000,000 live births. Hyperammonemic crises can be avoided in individuals with NAGS deficiency by the administration of carbamylglutamate (also known as carglumic acid), which activates carbamoyl phosphatase synthetase 1 (CPS1). The aim of this case series was to introduce additional cases of NAGS deficiency to the literature as well as to assess the role of nutrition management in conjunction with carbamylglutamate therapy across new and existing cases. METHODS: We conducted retrospective chart reviews of seven cases of NAGS deficiency in the US and Canada, focusing on presentation, diagnosis, medication management, nutrition management, and outcomes. RESULTS: Five new and two previously published cases were included. Presenting symptoms were consistent with previous reports. Diagnostic confirmation via molecular testing varied in protocol across cases, with consecutive single gene tests leading to long delays in diagnosis in some cases. All patients responded well to carbamylglutamate therapy, as indicated by normalization of plasma ammonia and citrulline, as well as urine orotic acid in patients with abnormal levels at baseline. Although protein restriction was not prescribed in any cases after carbamylglutamate initiation, two patients continued to self-restrict protein intake. One patient experienced two episodes of hyperammonemia that resulted in poor long-term outcomes. Both episodes occurred after a disruption in access to carbamylglutamate, once due to insurance prior authorization requirements and language barriers and once due to seizure activity limiting the family's ability to administer carbamylglutamate. CONCLUSIONS: Follow-up of patients with NAGS deficiency should include plans for illness and for disruption of carbamylglutamate access, including nutrition management strategies such as protein restriction. Carbamylglutamate can help patients with NAGS deficiency to liberalize their diets, but the maximum safe level of protein intake to prevent hyperammonemia is not yet known. Patients using this medication should still monitor their diet closely and be prepared for any disruptions in medication access, which might require immediate dietary adjustments or medical intervention to prevent hyperammonemia.

Evaluating change in diet with pegvaliase treatment in adults with phenylketonuria: Analysis of phase 3 clinical trial data.

Phenylketonuria (PKU), a genetic disorder characterized by phenylalanine hydroxylase (PAH) deficiency and phenylalanine (Phe) accumulation, is primarily managed with a protein-restricted diet and PKU-specific medical foods. Pegvaliase is an enzyme substitution therapy approved for individuals with PKU and uncontrolled blood Phe concentrations (>600 µmol/L) despite prior management. This analysis assessed the effect of pegvaliase on dietary intake using data from the Phase 3 PRISM-1 (NCT01819727), PRISM-2 (NCT01889862), and 165-304 (NCT03694353) clinical trials. Participants (N = 250) had a baseline diet assessment, blood Phe ≥600 µmol/L, and had discontinued sapropterin; they were not required to follow a Phe-restricted diet. Outcomes were analyzed by baseline dietary group, categorized as >75%, some (>0% but ≤75%), or no protein intake from medical food. At baseline, mean age was 29.1 years, 49.2% were female, mean body mass index was 28.4 kg/m2, and mean blood Phe was 1237.0 µmol/L. Total protein intake was stable up to 48 months for all 3 baseline dietary groups. Over this time, intact protein intake increased in all groups, and medical protein intake decreased in those who consumed any medical protein at baseline. Of participants consuming some or >75% medical protein at baseline, 49.1% and 34.1% were consuming no medical protein at last assessment, respectively. Following a first hypophenylalaninemia (HypoPhe; 2 consecutive blood Phe measurements <30 µmol/L) event, consumption of medical protein decreased and consumption of intact protein increased. Substantial and sustained Phe reductions were achieved in all 3 baseline dietary groups. The probability of achieving sustained Phe response (SPR) at ≤600 µmol/L was significantly greater for participants consuming medical protein versus no medical protein in an unadjusted analysis, but no statistically significant difference between groups was observed for probability of achieving SPR ≤360 or SPR ≤120 µmol/L. Participants with alopecia (n = 49) had longer pegvaliase treatment durations, reached HypoPhe sooner, and spent longer in HypoPhe than those who did not have alopecia. Most (87.8%) had an identifiable blood Phe drop before their first alopecia episode, and 51.0% (n = 21/41) of first alopecia episodes with known duration resolved before the end of the HypoPhe episode. In conclusion, pegvaliase treatment allowed adults with PKU to lower their blood Phe, reduce their reliance on medical protein, and increase their intact and total protein intake. Results also suggest that HypoPhe does not increase the risk of protein malnutrition in adults with PKU receiving pegvaliase.

The Effect of Preoperative Carbohydrate Intake on Length of Stay and Postoperative Recovery Following Laparoscopic Living Donor Nephrectomy.

OBJECTIVE: Enhanced Recovery After Surgery (ERAS) protocols are applied in many surgical procedures and often involve preoperative carbohydrate intake. Research surrounding the utility of ERAS in living donor nephrectomy is limited. The objective of this study was to identify whether living kidney donors who received preoperative oral carbohydrates experienced a difference in length of hospital stay (LOS), duration of time required to resume regular oral food and fluid intake, and incidence of gastrointestinal (GI) complications following laparoscopic nephrectomy compared to historical control donors who underwent preoperative fasting. METHODS: This study was a retrospective analysis of data from adult subjects at one transplant center who underwent laparoscopic living donor nephrectomy. A total of 55 ERAS subjects who received preoperative carbohydrates and 93 historical control subjects who underwent preoperative fasting were included in the final analysis. The following variables were compared between groups: LOS, time to tolerating a regular oral diet postoperatively, time to meeting 50% of estimated fluid needs by oral intake postoperatively, and incidence of postoperative GI complications. RESULTS: No significant differences between the ERAS and historical control groups in age, weight, body mass index, sex distribution, or estimated fluid needs were identified. Both groups consisted of predominantly female subjects. ERAS subjects experienced a shorter LOS (2.8 days versus 3.9 days, P < .001), time to tolerating a regular oral diet (36.5 hours versus 68.2 hours, P < .001), and time to meeting 50% of estimated fluid needs (25.3 hours versus 44.6 hours, P < .001) after laparoscopic nephrectomy compared to historical control subjects. No significant difference between groups in the incidence of postoperative GI complications (nausea, vomiting, or ileus) was identified. CONCLUSION: Our findings demonstrate the advantages of ERAS in living kidney donors undergoing laparoscopic nephrectomy and support ERAS implementation within this patient population.

Simplified Diet for nutrition management of phenylketonuria: A survey of U.S. metabolic dietitians.

BACKGROUND: Phenylketonuria (PKU) is an inherited metabolic disorder affecting the conversion of phenylalanine (Phe) to tyrosine. Medical nutrition therapy, consisting of a Phe-restricted diet with medical formula, is the primary treatment for PKU. The Simplified Diet is an approach to PKU nutrition management that allows certain fruits, vegetables, and low-protein foods to be eaten without measuring or tracking, referred to as free/uncounted foods. There is no consensus on how to implement this approach in metabolic centers in the United States (U.S.), and clinical practice varies. AIM: This study describes the clinical experience of metabolic dietitians in U.S.-based metabolic centers related to the use and implementation of the Simplified Diet. METHODS: A survey was developed and sent out to metabolic dietitians to query current clinical practices related to the Simplified Diet. Descriptive statistics were used to analyze responses. RESULTS: Sixty-three dietitians managing ≥5 patients with PKU in U.S.-based metabolic centers responded to the survey. Ninety-eight percent of survey respondents reported using some version of the Simplified Diet in clinical practice. The survey identified areas of strong agreement, including introduction of the Simplified Diet at 6 to 12 months of age. The survey also identified areas of widespread variability, including specific Phe or protein thresholds for free/uncounted foods, and whether or not to set daily quantity limits on these foods. CONCLUSIONS: Significant variability related to implementation of the Simplified Diet exists across U.S.-based metabolic centers. This practice variability may contribute to differences in the patient experience across centers and may indicate a need for development of clinical guidelines.

Bone Health in Classic Galactosemia: Systematic Review and Meta-Analysis.

INTRODUCTION: Previous studies have reported an association between classic galactosemia (CG) and decreased bone mass. The primary objective of this systematic review with meta-analysis was to determine the extent of bone mineral density (BMD) Z-score reduction. Low BMD was defined as a Z-score ≤-2 standard deviations (SD). The secondary objective was to evaluate other indicators of bone status through a descriptive analysis. METHODS: Systematic search strategies were developed by an experienced clinical librarian. Selection of relevant manuscripts, risk of bias assessment, and data extraction were performed independently by two investigators. RESULTS: Four studies were included in the meta-analysis. BMD Z-scores in children and adults with CG measured at the lumbar spine (LBMD; 4 studies; n  = 112), total hip (HBMD; 2 studies; n = 58), and femoral neck (FBMD; 2 studies; n = 73) were assessed. Mean BMD Z-scores in the CG population were LBMD -0.70 (95% CI: -0.88, -0.52); HBMD -0.89 (95% CI: -1.14, -0.64); and FBMD -0.63 (95% CI -1.29, 0.02). Results from studies included in the descriptive analysis (n = 7) show that vitamin D levels were frequently in the low reference range, whereas serum calcium levels were within reference range. CONCLUSION: The mean BMD Z-score in the CG population is -0.7, which is lower than in the general population, though still within two SD of the reference mean of zero. This indicates that bone health is mildly affected in CG and that more patients, compared to the general population, are at risk for a BMD Z-score ≤-2 SD. In conclusion, clinicians should ensure appropriate preventive and therapeutic measures for CG patients.

International clinical guideline for the management of classical galactosemia: diagnosis, treatment, and follow-up.

Classical galactosemia (CG) is an inborn error of galactose metabolism. Evidence-based guidelines for the treatment and follow-up of CG are currently lacking, and treatment and follow-up have been demonstrated to vary worldwide. To provide patients around the world the same state-of-the-art in care, members of The Galactosemia Network (GalNet) developed an evidence-based and internationally applicable guideline for the diagnosis, treatment, and follow-up of CG. The guideline was developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. A systematic review of the literature was performed, after key questions were formulated during an initial GalNet meeting. The first author and one of the working group experts conducted data-extraction. All experts were involved in data-extraction. Quality of the body of evidence was evaluated and recommendations were formulated. Whenever possible recommendations were evidence-based, if not they were based on expert opinion. Consensus was reached by multiple conference calls, consensus rounds via e-mail and a final consensus meeting. Recommendations addressing diagnosis, dietary treatment, biochemical monitoring, and follow-up of clinical complications were formulated. For all recommendations but one, full consensus was reached. A 93 % consensus was reached on the recommendation addressing age at start of bone density screening. During the development of this guideline, gaps of knowledge were identified in most fields of interest, foremost in the fields of treatment and follow-up.

Development of carrier testing for common inborn errors of metabolism in the Wisconsin Plain population.

PURPOSE: This community project is an initiative through the University of Wisconsin Biochemical Genetics Clinic and the Wisconsin Newborn Screening Program to identify members of the Plain population who are at risk for having children with maple syrup urine disease (MSUD) or propionic acidemia (PA) or who have PA. METHODS: Because of the high prevalence of metabolic conditions in the Plain population and the importance of early intervention, a statewide outreach project was developed to provide targeted variant analysis of the common MSUD and PA pathogenic variants in this population through health-care provider distribution of blood spot testing kits. Awareness was achieved through outreach efforts with the state midwives guild and Plain population meetings. RESULTS: Eighty individuals were tested; diagnosis was confirmed for three adults with PA and one couple was identified as being at risk for having a child with PA. Genetic counseling was provided to those identified. Follow-up diagnostic testing was completed for the at-risk couple's children; none were found to be affected. CONCLUSION: This initiative successfully provided accessible clinical testing for MSUD and PA for a high-risk population. Early identification of at-risk couples sets the foundation for early care of at-risk neonates, thereby improving future clinical outcomes.Genet Med 19 3, 352-356.

Metabolomic Insights into the Nutritional Status of Adults and Adolescents with Phenylketonuria Consuming a Low-Phenylalanine Diet in Combination with Amino Acid and Glycomacropeptide Medical Foods.

BACKGROUND: Nutrient status in phenylketonuria (PKU) requires surveillance due to the restrictive low-Phe diet in combination with amino acid medical foods (AA-MF) or glycomacropeptide medical foods (GMP-MF). Micronutrient profiles of medical foods are diverse, and optimal micronutrient supplementation in PKU has not been established. METHODS: In a crossover design, 30 participants with PKU were randomized to consume AA-MF and Glytactin™ GMP-MF in combination with a low-Phe diet for 3 weeks each. Fasting venipunctures, medical food logs, and 3-day food records were obtained. Metabolomic analyses were completed in plasma and urine by Metabolon, Inc. RESULTS: The low-Phe diets in combination with AA-MF and GMP-MF were generally adequate based on Dietary Reference Intakes, clinical measures, and metabolomics. Without micronutrient supplementation of medical foods, >70% of participants would have inadequate intakes for 11 micronutrients. Despite micronutrient supplementation of medical foods, inadequate intakes of potassium in 93% of participants and choline in >40% and excessive intakes of sodium in >63% of participants and folic acid in >27% were observed. Sugar intake was excessive and provided 27% of energy. CONCLUSIONS: Nutrient status was similar with AA-MF and Glytactin GMP-MF. More research related to micronutrient supplementation of medical foods for the management of PKU is needed.

Outcomes and genotype-phenotype correlations in 52 individuals with VLCAD deficiency diagnosed by NBS and enrolled in the IBEM-IS database.

Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency can present at various ages from the neonatal period to adulthood, and poses the greatest risk of complications during intercurrent illness or after prolonged fasting. Early diagnosis, treatment, and surveillance can reduce mortality; hence, the disorder is included in the newborn Recommended Uniform Screening Panel (RUSP) in the United States. The Inborn Errors of Metabolism Information System (IBEM-IS) was established in 2007 to collect longitudinal information on individuals with inborn errors of metabolism included in newborn screening (NBS) programs, including VLCAD deficiency. We retrospectively analyzed early outcomes for individuals who were diagnosed with VLCAD deficiency by NBS and describe initial presentations, diagnosis, clinical outcomes and treatment in a cohort of 52 individuals ages 1-18years. Maternal prenatal symptoms were not reported, and most newborns remained asymptomatic. Cardiomyopathy was uncommon in the cohort, diagnosed in 2/52 cases. Elevations in creatine kinase were a common finding, and usually first occurred during the toddler period (1-3years of age). Diagnostic evaluations required several testing modalities, most commonly plasma acylcarnitine profiles and molecular testing. Functional testing, including fibroblast acylcarnitine profiling and white blood cell or fibroblast enzyme assay, is a useful diagnostic adjunct if uncharacterized mutations are identified.

Abnormal Eating Behaviors Are Common in Children with Fetal Alcohol Spectrum Disorder.

OBJECTIVE: To compare the eating behaviors and nutrition-related concerns in children with fetal alcohol spectrum disorder (FASD) with those in typically developing children. STUDY DESIGN: A survey that assessed eating behaviors was completed between October 2013 and May 2014 by the caregivers of children screened for FASD at the University of Minnesota's Fetal Alcohol Spectrum Disorders Program, and typically developing children recruited from that clinic or from the Research Participation Core of the Waisman Center, University of Wisconsin. RESULTS: Compared with controls (N = 81), children with FASD (N = 74) had delayed acquisition of self-feeding behavior (P < .001) and solid food introduction (P < .001). Impaired satiety was common and independent of medication use: 23.0% were never full/satisfied, 31.1% snacked constantly, and 27.0% concealed food (all P ≤ .002). They consumed the equivalent of an additional meal/snack daily (P < .01). Children with FASD were more likely to have a past diagnosis of underweight (P < .001). Mean body mass index was significantly reduced for males (P = .009) but not females (P = .775) with FASD, and only 2 children with FASD were currently underweight. Children with FASD were more physically active (P < .01). CONCLUSIONS: Abnormal eating patterns are common in children with FASD and may contribute to their delayed growth and nutritional inadequacies. Their poor satiety may reflect poor impulse control. Children with FASD may benefit from diet counseling. Conversely, some children with hyperphagia may warrant referral for FASD screening.

Successful pregnancy and delivery in a woman with propionic acidemia from the Amish community.

Propionic acidemia (PA) is an inborn error of protein metabolism with a variable clinical presentation ranging from neonatal encephalopathy to seemingly asymptomatic individuals who present with cardiomyopathy or sudden death. PA is recognized in the Amish population, often with an early asymptomatic course and eventual cardiac complications. Thus, Amish women with PA may reach reproductive age without clinical sequelae, but are at increased risk for metabolic decompensation during pregnancy, delivery and postpartum period. We describe the care of an Amish woman with PA during her first pregnancy and delivery.

Rhabdomyolysis in a neonate due to very long chain acyl CoA dehydrogenase deficiency.

Very long chain acyl CoA dehydrogenase deficiency (VLCADD) is an inborn error in long chain fatty acid oxidation with significant variability in the severity and timing of its clinical presentation. Neonatal presentations of VLCADD have included hypoglycemia and cardiomyopathy while rhabdomyolysis is usually a later onset complication. We describe a neonate with VLCADD presenting with rhabdomyolysis prior to the return of an abnormal newborn screen. This report suggests that evaluating for rhabdomyolysis, in addition to a cardiac and hepatic work-up, is an important part of the initial evaluation of an infant with an abnormal newborn screen suggesting a diagnosis of VLCADD.

A re-evaluation of life-long severe galactose restriction for the nutrition management of classic galactosemia.

The galactose-restricted diet is life-saving for infants with classic galactosemia. However, the benefit and extent of dietary galactose restriction required after infancy remain unclear and variation exists in practice. There is a need for evidence-based recommendations to better standardize treatment for this disorder. This paper reviews the association between diet treatment and outcomes in classic galactosemia and evaluates the contribution of food sources of free galactose in the diet. Recommendations include allowing all fruits, vegetables, legumes, soy products that are not fermented, various aged cheeses and foods containing caseinates. Further research directions are discussed.

Galactose content of legumes, caseinates, and some hard cheeses: implications for diet treatment of classic galactosemia.

There are inconsistent reports on the lactose and/or galactose content of some foods traditionally restricted from the diet for classic galactosemia. Therefore, samples of cheeses, caseinates, and canned black, pinto, kidney, and garbanzo beans were analyzed for free galactose content using HPLC with refractive index or pulsed amperometric detection. Galactose concentrations in several hard and aged cheeses and three mild/medium Cheddars, produced by smaller local dairies, was <10 mg/100 g sample compared to 55.4 mg/100 g sample in four sharp Cheddars produced by a multinational producer. Galactose in sodium and calcium caseinate ranged from undetectable to 95.5 mg/100 g sample. Free galactose level in garbanzo beans was lower than previously reported at 24.6 mg/100 g sample; black beans contained 5.3 mg/100 g, and free galactose was not detected in red kidney or pinto beans. These data provide a basis for recommending inclusion of legumes, caseinate-containing foods, and some aged hard cheeses that had been previously restricted in the diet for individuals with galactosemia.

Recommendations for the nutrition management of phenylalanine hydroxylase deficiency.

The effectiveness of a phenylalanine-restricted diet to improve the outcome of individuals with phenylalanine hydroxylase deficiency (OMIM no. 261600) has been recognized since the first patients were treated 60 years ago. However, the treatment regime is complex, costly, and often difficult to maintain for the long term. Improvements and refinements in the diet for phenylalanine hydroxylase deficiency have been made over the years, and adjunctive therapies have proven to be successful for certain patients. Yet evidence-based guidelines for managing phenylalanine hydroxylase deficiency, optimizing outcomes, and addressing all available therapies are lacking. Thus, recommendations for nutrition management were developed using evidence from peer-reviewed publications, gray literature, and consensus surveys. The areas investigated included choice of appropriate medical foods, integration of adjunctive therapies, treatment during pregnancy, monitoring of nutritional and clinical markers, prevention of nutrient deficiencies, providing of access to care, and compliance strategies. This process has not only provided assessment and refinement of current nutrition management and monitoring recommendations but also charted a direction for future studies. This document serves as a companion to the concurrently published American College of Medical Genetics and Genomics guideline for the medical treatment of phenylalanine hydroxylase deficiency.

Inappropriate feeding behaviors and dietary intakes in children with fetal alcohol spectrum disorder or probable prenatal alcohol exposure.

BACKGROUND: Prenatal alcohol exposure (PAE) is a leading cause of significant neurobehavioral and neurocognitive deficits. Its potential consequences for eating behaviors, nutritional status, and other nutritional issues in childhood have received little attention. METHODS: Nineteen children (11 boys, 8 girls) of mean age 9.6 years, referred for fetal alcohol spectrum disorder (FASD) screening and assessment, were analyzed with physical exams and caregiver questionnaires to identify possible abnormalities in food and eating behaviors. Fourteen children contributed 24-hour diet recalls and were assessed for nutritional status. RESULTS: Seventy-nine percent of participants were diagnosed with FASD and 63.2% had confirmed PAE. Fifty percent of girls were overweight or obese, whereas 37% of boys had reduced stature, weight, or body mass index for their age. Recurring feeding problems included constant snacking (36.8%), lack of satiety (26.3%), and picky eating/poor appetite (31.6%). None had oral feeding problems. Constipation was common (26.3%). Macronutrient intakes were largely normal, but sugar consumption was excessive (140 to 190% of recommendations) in 57% of subjects. Vitamin A intake exceeded the upper limit for 64% of participants, whereas ≥50% had intakes <80% of recommended daily allowances (RDAs) for choline, vitamin E, potassium, ß-carotene, and essential fatty acids; 100% had vitamin D intakes <80% of the RDA. CONCLUSIONS: PAE may be associated with altered acquisition and distribution of body mass with increasing age. Disordered eating was common. The increased feeding behaviors surrounding lack of satiety suggest that self-regulation may be altered. Constipation could reflect low dietary fiber or altered gastrointestinal function. These exploratory data suggest that children with PAE may be at risk for nutritional deficiencies, which are influenced by inappropriate food preferences, disordered eating patterns, medication use, and the stressful dynamics surrounding food preparation and mealtime.

Prevalence and mutation analysis of short/branched chain acyl-CoA dehydrogenase deficiency (SBCADD) detected on newborn screening in Wisconsin.

Short/branched chain acyl-CoA dehydrogenase deficiency (SBCADD), also called 2-methylbutyryl CoA dehydrogenase deficiency (2-MBCDD), is a disorder of l-isoleucine metabolism of uncertain clinical significance. SBCADD is inadvertently detected on expanded newborn screening by elevated 2-methylbutyrylcarnitine (C5), which has the same mass to charge (m/s) on tandem mass spectrometry (MS/MS) as isovalerylcarnitine (C5), an analyte that is elevated in isovaleric acidemia (IVA), a disorder in leucine metabolism. SBCADD cases identified in the Hmong-American population have been found in association with the c.1165 A>G mutation in the ACADSB gene. The purposes of this study were to: (a) estimate the prevalence of SBCADD and carrier frequency of the c.1165 A>G mutation in the Hmong ethnic group; (b) determine whether the c.1165 A>G mutation is common to all Hmong newborns screening positive for SBCADD; and (c) evaluate C5 acylcarnitine cut-off values to detect and distinguish between SBCADD and IVA diagnoses. During the first 10years of expanded newborn screening using MS/MS in Wisconsin (2001-2011), 97 infants had elevated C5 values (≥0.44µmol/L), of whom five were Caucasian infants confirmed to have IVA. Of the remaining 92 confirmed SBCADD cases, 90 were of Hmong descent. Mutation analysis was completed on an anonymous, random sample of newborn screening cards (n=1139) from Hmong infants. Fifteen infants, including nine who had screened positive for SBCADD based on a C5 acylcarnitine concentration ≥0.44µmol/L, were homozygous for the c.1165 A>G mutation. This corresponds to a prevalence in this ethnic group of being homozygous for the mutation of 1.3% (95% confidence interval 0.8-2.2%) and of being heterozygous for the mutation of 21.8% (95% confidence interval 19.4-24.3%), which is consistent with the Hardy-Weinberg equilibrium. Detection of homozygous individuals who were not identified on newborn screening suggests that the C5 screening cut-off would need to be as low as 0.20µmol/L to detect all infants homozygous for the ACADSB c.1165 A>G mutation. However, lowering the screening cut-off to 0.20 would also result in five "false positive" (non-homozygous) screening results in the Hmong population for every c.1165 A>G homozygote detected. Increasing the cut-off to 0.60µmol/L and requiring elevated C5/C2 (acetylcarnitine) and C5/C3 (propionylcarnitine) ratios to flag a screen as abnormal would reduce the number of infants screening positive, but would still result in an estimated 5 infants with SBCADD per year who would require follow-up and additional biochemical testing to distinguish between SBCADD and IVA diagnoses. Further research is needed to determine the clinical outcomes of SBCADD detected on newborn screening and the c.1165 A>G mutation before knowing whether the optimal screening cut-off would minimize true positives or false negatives for SBCADD associated with this mutation.

Newborn screening 50 years later: access issues faced by adults with PKU.

Fifty years after the implementation of universal newborn screening programs for phenylketonuria, the first disease identified through newborn screening and considered a success story of newborn screening, a cohort of adults with phenylketonuria treated from birth provides valuable information about effects of long-term treatment for inborn errors of metabolism in general, and phenylketonuria specifically. For phenylketonuria, newborn screening allows early implementation of the phenylalanine-restricted diet, eliminating the severe neurocognitive and neuromotor impairment associated with untreated phenylketonuria. However, executive function impairments and psychiatric problems are frequently reported even for those treated early and continuously with the phenylalanine-restricted diet alone. Moreover, a large percentage of adults with phenylketonuria are reported as lost to follow-up by metabolic clinics. While a group of experts identified by the National Institutes of Health convenes to update treatment guidelines for phenylketonuria, we explore individual patient, social, and economic factors preventing >70% of adult phenylketonuria patients in the United States from accessing treatment. As more conditions are identified through newborn screening, factors affecting access to treatment grow in importance, and we must continue to be vigilant in assessing and addressing factors that affect patient treatment outcomes and not just celebrate amelioration of the most severe manifestations of disease.

Food products made with glycomacropeptide, a low-phenylalanine whey protein, provide a new alternative to amino Acid-based medical foods for nutrition management of phenylketonuria.

Phenylketonuria (PKU), an inborn error in phenylalanine metabolism, requires lifelong nutrition management with a low-phenylalanine diet, which includes a phenylalanine-free amino acid-based medical formula to provide the majority of an individual's protein needs. Compliance with this diet is often difficult for older children, adolescents, and adults with PKU. The whey protein glycomacropeptide (GMP) is ideally suited for the PKU diet because it is naturally low in phenylalanine. Nutritionally complete, acceptable medical foods and beverages can be made with GMP to increase the variety of protein sources for the PKU diet. As an intact protein, GMP improves protein use and increases satiety compared with amino acids. Thus, GMP provides a new, more physiologic source of low-phenylalanine dietary protein for people with PKU.