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Background: Metabolic control in phenylketonuria (PKU) is known to deteriorate with age, but national-level data describing blood phenylalanine (Phe) control across the United Kingdom (UK) are limited. Objective: To characterise blood Phe control in individuals with PKU attending UK metabolic centres. Methods: Sixteen UK centres (nine paediatric, six adult, one mixed) retrospectively extracted blood Phe results collected between 2012 and 2018. Demographic, phenotypic and monitoring-related variables were analysed. Written consent for data collection was obtained from all patients or their caregivers. Results: Data were available for 871 individuals (55% female), of whom 744 (85%) were classified as follows: classical PKU, 75%, mild PKU, 22% and hyperphenylalaninaemia, 3%. Mean blood Phe concentrations were significantly higher in adults than children (491 ± 308 vs. 303 ± 199 µmol/L; p < 0.001), and the proportion of samples within target range declined steadily with age, from 78% in children < 2 years to 36% in adults ≥ 41 years. Individuals with classical PKU had higher mean Phe concentrations and lower target attainment than those with HPA (386 vs. 300 µmol/L; 61% vs. 78%; p < 0.001), while mild PKU and HPA showed comparable control. Females generally demonstrated better metabolic control than males. More frequent dried blood spot sampling for blood Phe was strongly associated with improved metabolic control: weekly (254 ± 175 µmol/L; 82% within target), fortnightly (319 ± 207 µmol/L; 70%), monthly (397 ± 231 µmol/L; 61%), and less than monthly (624 ± 349 µmol/L; 44%). Nearly half of the blood Phe samples (47%) with recorded timing were taken in a non-fasting state. Conclusions: Achieving lifelong metabolic stability on a Phe-restricted diet alone remains challenging. These national data highlight the need for broader therapeutic options to support individuals with PKU across the lifespan.

Arginase deficiency is a rare autosomal recessive urea cycle disorder (UCD) caused by mutations in the ARG1 gene encoding arginase that catalyses the hydrolysis of arginine to ornithine and urea. Patients have hyperargininaemia and progressive neurological impairment but generally suffer fewer metabolic decompensations compared to other UCDs. The objective is to describe the clinical features, biochemical profile, neuroradiological findings and experience of managing children with arginase deficiency. Twenty‐year retrospective review of patient medical records at a single metabolic centre was performed. Six patients from three unrelated families were identified. Mean age at first symptom was 3.3 (1.5–9.0) years, while mean age at diagnosis was 8.8 (0.16–15.92) years. Four patients developed spastic diplegia and two of six with spastic quadriplegia with classical features including hyperreflexia, clonus and toe walking. This resulted in gait abnormalities that have been monitored using the GAITRite system and required Achilles tendon release in five children. Generalised tonic‐clonic seizures and/or absences were present in three of six children and were controlled with anticonvulsants. All patients had moderate learning difficulties. Neuroimaging showed cerebral/cerebellar atrophy in four patients and basal ganglia abnormalities in two. Arginine levels were universally elevated throughout follow‐up despite protein restriction, essential amino acid supplementation and ammonia scavengers, and neurological outcome was generally poor. Two patients died following severe metabolic decompensation in adolescence. Children with arginase deficiency continue to present a management challenge of what appears to be an inexorable course of neurocognitive impairment. Further insight into disease mechanisms may provide insight into novel treatment strategies.

BackgroundDisorders of AA metabolism require dietary protein restriction, l-amino acid supplementation and low-protein (LP) prescribed foods for metabolic control. The overall cost of LP diets to the NHS is estimated to be in the region of £12,000 to £18,000 per Phenylketonuria (PKU) patient per year, with costs varying according to patient age. Approximately 20% of this cost is attributed to food. Therefore, cost of LP foods for our PKU cohort (n=180) can be estimated to be in the region of £432,000 to £648,000 per year. Appropriate prescribing of LP foods is essential in a financially pressured NHS.MethodWe collated a cost list of ACBS-endorsed LP foods (n=146) from 9 food manufacturers. Prices were obtained from the online BNF, or if unavailable from food manufacturer representatives. Foods were grouped into 19 categories according to type.ResultsPrices were obtained for all foods, from the BNF (49%) or manufacturer representatives (51%). There was a wide range in costs both average costs within a category and between categories. Bread loaves were the cheapest (median £0.83/100g); savoury (burger/sausage/potato cake) mixes were the most expensive (median £5.31/100g). The biggest price range per 100g were crackers/crispbreads (£4.89) and biscuits (£4.11). Breakfast bars had the smallest price range per 100g (£0.34), but a high average cost. Comparing the cheapest and most expensive items in five basic ingredient categories (bread loaf, pasta, flour mix, biscuits, desserts) a prescription could range from £30.60 to £51.64.DiscussionA lack of transparency and wide variation in costs are two major barriers to cost effective prescribing. This situation requires dietitians to be knowledgeable about up to date food prices. Savings could be made if price information was easily available through the BNF for all LP foods. Balancing cost with patient choice is a challenge in clinical practice.

BackgroundMorbidity remains high in MMAmut0 patients. Liver transplantation can decrease metabolic decompensation episodes and organ damage whilst improving quality of life (QOL).Case reportAn infant was prospectively managed as family history of MMAmut0, and confirmed postnatally. Bilateral dysplastic multicystic kidneys were diagnosed after birth and hepatoblastoma at 4 months. He underwent liver transplant age 6 months for tumour removal and MMA management.Pre-transplantDue to low albumin (<20 g/L), poor weight gain (0.4th-2nd to < 0.4th centile), protein was increased, 2 to 2.4 g/kg/d (WHO 2007, safe intake (SI) 1.77 g/kg/d), energy 120 to 140kcal/kg/d. He fed orally with NG top-ups. Poor feed tolerance necessitated a hydrolysed feed. Parenteral nutrition (PN) was required twice because of vomiting. Age 12 weeks protein was decreased, 1.85 g/kg/d as ammonia remained high (120-148umol/L). He thrived (weight, length 25th -50thcentile). Median plasma MMA (pMMA) was 134umol/L (range 44.2-230), (ref range 0-0.29).Post-transplantPN matched pre-transplant protein and energy intakes. He recommenced hydrolysed feed, via NGT and orally. After 3 months pMMA remained elevated, median 125umol/L (range 76.9- 169) protein was reduced to 1.5 g/kg/d (SI 1.14 g/kg/d) and is unchanged 1year post-transplant. All feeds are taken orally.ConclusionEpisodes of metabolic decompensation markedly decreased. Parents report QOL improved. Protein remains restricted.

Background: Special low-protein foods are essential in the dietary treatment of phenylketonuria (PKU). In the UK, these are available on prescription through the General Practitioners (GPs) and distributed via nutritional home delivery companies or pharmacies. Methods: A 58-item online non-validated semi-structured questionnaire was emailed to British Inherited Metabolic Disease Group (BIMDG) dietitians and dietetic support workers (DSW)/administrators working in PKU to ascertain the main system issues and errors with the supply of low-protein prescription foods (LPPF). Results: 73% (n = 53/73) of dietitians and 72% (n = 18/25) of DSW/administrators responded. A total of 80 questionnaires (representing 44 paediatric and 36 adult PKU centres) were completed. A total of 50% (n = 40/80) of respondents reported patient/caregiver problems accessing LPPF at least weekly. The most common problems were unavailable products (82%), missing LPPF in deliveries (79%), and delayed deliveries (66%). For 64% of respondents, >25% of their patients had recurring problems accessing LPPF, and 69% of respondents spent ≥1 h/week and 11% >5 h/week correcting LPPF patient supply issues. The most common foods patients experienced supply issues with were bread (96%), pasta/rice (41%) and milk replacements (35%). This was associated with GP prescription errors (65%), LPPF prescriptions sent to incorrect dispensers/suppliers (60%), and manufacturer supply issues (54%). Problems with patients/caregivers included not ordering LPPF in a timely way (81%), not responding to messages from home delivery companies (73%) and poor understanding of the ordering process (70%). The majority (93%) of respondents reported that prescription issues impacted their patients’ blood Phe control. Suggestions for improving access to LPPF included centralisation of the system to one supplier (76%) and apps for ordering LPPF (69%). Conclusions: The supply of LPPF for PKU in the UK is problematic; it may adversely affect the ability of patients to adhere to dietary management, and a review investigating patient access to LPPF is urgently required.

The nutritional and metabolic characteristics of adult phenylketonuria (PKU) patients in the UK with varying dietary adherence is unknown. In other countries, nutritional and metabolic abnormalities have been reported in nonadherent patients compared to adherent counterparts. A pooled analysis of primary baseline data from two UK multi-centre studies was therefore performed to establish whether this is true from a UK perspective. Adult PKU patients who had provided 3-day food records and amino acid blood samples were included and grouped according to dietary adherence (adherent; n = 16 vs. nonadherent; n = 14). Nonadherent patients consumed greater amounts of natural protein compared to adherent patients (61.6 ± 30.7 vs. 18.3 ± 7.7 g/day; q < 0.001). In contrast, the contribution of protein substitutes to total protein intake was lower in nonadherent compared to adherent patients (3.9 ± 9.2 g/day vs. 58.6 ± 10.2 g/day; q < 0.001). Intakes of iron, zinc, vitamin D3, magnesium, calcium, selenium, iodine, vitamin C, vitamin A and copper were significantly lower in nonadherent compared to adherent patients and were below UK Reference Nutrient Intakes. Similarly, intakes of thiamin, riboflavin, niacin, vitamin B6 and phosphorus were significantly lower in nonadherent compared to adherent patients but met the UK Reference Nutrient Intakes. Phenylalanine concentrations in nonadherent patients were significantly higher than adherent patients (861 ± 348 vs. 464 ± 196 µmol/L; q = 0.040) and fell outside of European treatment target ranges. This study shows the nutritional and metabolic consequences of deviation from phenylalanine restriction and intake of PKU protein substitutes in nonadherent adult PKU patients. Collectively, these data further underlie the importance of life-long adherence to the PKU diet.

(1) Background: Good adherence to a Phe-restricted diet supplemented with an adequate amount of a protein substitute (PS) is important for good clinical outcomes in PKU. Glycomacropeptide (cGMP)-PSs are innovative, palatable alternatives to amino acid-based PSs (AA-PS). This study aimed to evaluate a new cGMP-PS in liquid and powder formats in PKU. (2) Methods: Children and adults with PKU recruited from eight centres were prescribed at least one serving/day of cGMP-PS for 7–28 days. Adherence, acceptability, and gastrointestinal tolerance were recorded at baseline and the end of the intervention. The blood Phe levels reported as part of routine care during the intervention were recorded. (3) Results: In total, 23 patients (powder group, n = 13; liquid group, n = 10) completed the study. The majority assessed the products to be palatable (77% of powder group; 100% of liquid group) and well tolerated; the adherence to the product prescription was good. A total of 14 patients provided blood Phe results during the intervention, which were within the target therapeutic range for most patients (n = 11) at baseline and during the intervention. (4) Conclusions: These new cGMP-PSs were well accepted and tolerated, and their use did not adversely affect blood Phe control.

Patients with phenylketonuria (PKU) are reliant on special low protein foods (SLPFs) as part of their dietary treatment. In England, several issues regarding the accessibility of SLPFs through the national prescribing system have been highlighted. Therefore, prescribing patterns and expenditure on all SLPFs available on prescription in England (n = 142) were examined. Their costs in comparison to regular protein-containing (n = 182) and ‘free-from’ products (n = 135) were also analysed. Similar foods were grouped into subgroups (n = 40). The number of units and costs of SLPFs prescribed in total and per subgroup from January to December 2020 were calculated using National Health Service (NHS) Business Service Authority (NHSBSA) ePACT2 (electronic Prescribing Analysis and Cost Tool) for England. Monthly patient SLPF units prescribed were calculated using patient numbers with PKU and non-PKU inherited metabolic disorders (IMD) consuming SLPFs. This was compared to the National Society for PKU (NSPKU) prescribing guidance. Ninety-eight percent of SLPF subgroups (n = 39/40) were more expensive than regular and ‘free-from’ food subgroups. However, costs to prescribe SLPFs are significantly less than theoretical calculations. From January to December 2020, 208,932 units of SLPFs were prescribed (excluding milk replacers), costing the NHS £2,151,973 (including milk replacers). This equates to £962 per patient annually, and prescribed amounts are well below the upper limits suggested by the NSPKU, indicating under prescribing of SLPFs. It is recommended that a simpler and improved system should be implemented. Ideally, specialist metabolic dietitians should have responsibility for prescribing SLPFs. This would ensure that patients with PKU have the necessary access to their essential dietary treatment, which, in turn, should help promote dietary adherence and improve metabolic control.

(1) Background: Poor palatability, large volume, and lack of variety of some liquid and powdered protein substitutes (PSs) for patients with phenylketonuria (PKU) and tyrosinemia (TYR) can result in poor adherence. This study aimed to evaluate a new unflavoured, powdered GMP-based PS designed to be mixed into drinks, foods, or with other PSs, in patients with PKU and TYR. (2) Methods: Paediatric and adult community-based patients were recruited from eight metabolic centres and prescribed ≥1 sachet/day (10 g protein equivalent (PE)) of the Mix-In-style PS over 28 days. Adherence, palatability, GI tolerance, and metabolic control were recorded at baseline and follow-up. Patients who completed at least 7 days of intervention were included in the final analysis. (3) Results: Eighteen patients (3–45 years, nine males) with PKU (n = 12) and TYR (n = 6) used the Mix-In-style PS for ≥7 days (mean 26.4 days (SD 4.6), range 11–28 days) alongside their previous PS, with a mean intake of 16.7 g (SD 7.7) PE/day. Adherence was 86% (SD 25), and GI tolerance was stable, with n = 14 experiencing no/no new symptoms and n = 3 showing improved symptoms compared to baseline. Overall palatability was rated satisfactory by 78% of patients, who successfully used the Mix-In-style PS in various foods and drinks, including smoothies, squash, and milk alternatives, as a top-up to meet their protein needs. There was no concern regarding safety/metabolic control during the intervention. (4) Conclusions: The ‘Mix-In’-style PS was well adhered to, accepted, and tolerated. Collectively, these data show that providing a flexible, convenient, and novel format of PS can help with adherence and meet patients’ protein needs.

In the UK, different dietary systems are used to calculate protein or tyrosine/phenylalanine intake in the dietary management of hereditary tyrosinaemia, HTI, II and III (HT), with no systematic evidence comparing the merits and inadequacies of each. This study aimed to examine the current UK dietary practices in all HTs and, using Delphi methodology, to reach consensus agreement about the best dietary management system. Over 12 months, five meetings were held with UK paediatric and adult dietitians working in inherited metabolic disorders (IMDs) managing HTs. Eleven statements on the dietary system for calculating protein or tyrosine/phenylalanine intake were discussed. Dietitians from 12 of 14 IMD centres caring for HT patients participated, and 7/11 statements were agreed with one Delphi round. Nine centres (three abstentions) supported a 1 g protein exchange system for all foods except fruit and vegetables. The same definitions used in the UK for phenylketonuria (PKU) were adopted to define when to calculate foods as part of a protein exchange system or permit them without measurement. Fruit and vegetables contain a lower amount of tyrosine/phenylalanine per 1 g of protein than animal and cereal foods. The correlation of tyrosine vs. phenylalanine (mg/100 g) for vegetables and fruits was high (r = 0.9). In Delphi round 2, agreement was reached to use the tyrosine/phenylalanine analyses of fruits/vegetables, for their allocation within the HT diet. This allowed larger portion sizes of measured fruits and vegetables and increased the variety of fruit and vegetables that could be eaten without measurement. In HTs, a combined dietary management system will be used: 1 g protein exchanges for cereal and milk protein sources and tyrosine/phenylalanine exchanges for fruit and vegetables. Intensive, systematic communication with IMD dietitians and reappraisal of the evidence has redefined and harmonised HT dietary practice across the UK.