Treatment adherence during childhood in individuals with phenylketonuria: Early signs of treatment discontinuation

Introduction: Phenylketonuria (PKU) is an autosomal recessive disorder characterized by a deficiency in phenylalanine (Phe) hydroxylase activity. Early diagnosis and continuous treatment with a low Phe diet prevents severe neurological and cognitive impairment. Aims 1. Analyze how treatment adherence evolves through infancy, childhood, and early adolescence in individuals with PKU. 2. Identify early signs of treatment discontinuation. Methodology This longitudinal, retrospective study included 75 children diagnosed through newborn screening, ages 7 to 13 years. Data on blood Phe concentration, number of blood samples sent, proportion of samples with Phe concentrations over the recommended range, and number of visits to the metabolism clinic were recorded. Logistic regression analysis was used to identify the variables that predict treatment discontinuation before 13 years of age. Results: A progressive increase in mean blood Phe concentrations with age was identified. The greatest increase occurred between the first and second years of life. By age ten, mean Phe blood concentration of the group was above the recommended range. The proportion of samples with Phe concentrations over the recommended range also increased with age, from an average of 13% during the first year of life to 67% in early adolescence. Sixty-eight percent of the children attended the outpatient clinic and sent samples from birth to the time of the study. Individuals who discontinued follow-up showed significantly higher mean blood Phe concentrations (360 vs. 220.9 μmol/L; p = 0.004) and the proportion of samples over the recommended range (37% vs. 12% p = 0.002) was significantly higher during the second year of life. Mean age for children who discontinued treatment was 5.5 years of age. Blood Phe concentration values at 12 to 23 months of age and at 6 to 8 years of age significantly predicted treatment discontinuation before 13 years of age. Conclusion: Treatment adherence in PKU diminishes with age. Early signs of treatment discontinuation can be identified during the second year of life, allowing preventive interventions in high risk groups

Long-term effects of medical management on growth and weight in individuals with urea cycle disorders

Low protein diet and sodium or glycerol phenylbutyrate, two pillars of recommended long-term therapy of individuals with urea cycle disorders (UCDs), involve the risk of iatrogenic growth failure. Limited evidence-based studies hamper our knowledge on the long-term effects of the proposed medical management in individuals with UCDs. We studied the impact of medical management on growth and weight development in 307 individuals longitudinally followed by the Urea Cycle Disorders Consortium (UCDC) and the European registry and network for Intoxication type Metabolic Diseases (E-IMD). Intrauterine growth of all investigated UCDs and postnatal linear growth of asymptomatic individuals remained unaffected. Symptomatic individuals were at risk of progressive growth retardation independent from the underlying disease and the degree of natural protein restriction. Growth impairment was determined by disease severity and associated with reduced or borderline plasma branched-chain amino acid (BCAA) concentrations. Liver transplantation appeared to have a beneficial effect on growth. Weight development remained unaffected both in asymptomatic and symptomatic individuals. Progressive growth impairment depends on disease severity and plasma BCAA concentrations, but cannot be predicted by the amount of natural protein intake alone. Future clinical trials are necessary to evaluate whether supplementation with BCAAs might improve growth in UCDs

Biochemical markers and neuropsychological functioning in distal urea cycle disorders

Urea cycle disorders often present as devastating metabolic conditions, resulting in high mortality and significant neuropsychological damage, despite treatment. The Urea Cycle Disorders Longitudinal Study is a natural history study that collects data from regular clinical follow-up and neuropsychological testing. This report examines links between biochemical markers (ammonia, glutamine, arginine, citrulline) and primary neuropsychological endpoints in three distal disorders, argininosuccinic acid synthetase deficiency (ASD or citrullinemia type I), argininosuccinic acid lyase deficiency (ASA or ALD), and arginase deficiency (ARGD). Laboratory results and test scores from neuropsychological evaluations were assessed in 145 study participants, ages 3 years and older, with ASD (n = 64), ASA (n = 65) and ARGD (n = 16). Mean full scale IQ was below the population mean of 100 ± 15 for all groups: (ASD = 79 ± 24; ASA = 71 ± 21; ARGD = 65 ± 19). The greatest deficits were noted in visual performance and motor skills for all groups. While ammonia levels remain prominent as prognostic biomarkers, other biomarkers may be equally valuable as correlates of neuropsychological functioning. Cumulative exposure to the biomarkers included in the study proved to be highly sensitive indicators of neuropsychological outcomes, even when below the cut-off levels generally considered toxic. Blood levels of biomarkers obtained on the day of neuropsychological evaluations were not correlated with measures of functioning for any disorder in any domain. The importance of cumulative exposure supports early identification and confirms the need for well-controlled management of all biochemical abnormalities (and not just ammonia) that occur in urea cycle disorders

Cognitive functioning in mild hyperphenylalaninemia

Background: Hyperphenylalaninemia is a hereditary metabolic disorder that causes elevated blood phenylalanine (Phe). Hyperphenylalaninemias are classified as Phenylketonuria PKU (Phe > 6 mg/dL) or mild hyperphenylalaninemia (mHPA) (Phe 2–6 mg/dL). This study examines the cognitive functioning of early diagnosed children with mHPA compared with early diagnosed and treated children with PKU. Sample and methods: Psychomotor development (BSID-II) at 12 and 36 months of age, and cognitive performance at 4 and 7 years of age (WPPSI and WISC-R), were assessed in 118 PKU and 97 mHPA patients. Cognitive profile analysis of WISC-R subscales in school age children was performed and results were compared between the two groups. Results: Both groups preformed within the average range. Scores were significantly higher in the mHPA group. The mean Mental Development Index (MDI) at 12 months of age was 98.1 in the mHPA group and 92.3 in the PKU group (p < 0.0002). At 36 months the MDI was 94.6 in the mHPA group and 84.7 in the PKU group (p = 0.0001. At age four years the mean Full Scale IQ was 106.5 (mHPA group) and 95.9 (PKU group) (p < 0.0001). At age seven years the mean Full Scale IQ was 100.9 (mHPA group) and 89.9 (PKU group) (p < 0.005). The pattern of deficits was similar in both groups, with relative weaknesses in working memory and attention. Conclusions: Children with mHPA achieved cognitive performance well within the average range and attained significantly higher scores than children with PKU. However, they appeared to have relative weaknesses in working memory and attention, similar to children with PKU

Adaptation and Validation of a Questionnaire to Evaluate Knowledge of the Low Phe Diet in PKU.

Phenylketonuria (PKU) is an autosomal recessive disorder of phenylalanine (Phe) metabolism, causing a build-up of Phe in the body. Treatment consists of a Phe-restricted diet for life and regular determination of blood Phe levels to monitor the intake of Phe. Despite the fact that diet is the cornerstone of treatment, there are no studies examining common knowledge about food items and whether they are allowed as part of the PKU diet. Improving parents' and patients' knowledge and competence about the diet enables them to make appropriate food choices. This study validates a food-knowledge questionnaire first developed in Spanish and modified for English speaking populations. The questionnaire potentially helps parents to prepare appropriate meals and healthcare providers to create individualized educational programs about PKU for children and adolescents with this disorder

In the Early Postpartum Period, Parents are Interested in Newborn Genomic Testing

Purpose We surveyed parents to ascertain interest in newborn genomic testing and determine whether these queries would provoke refusal of conventional newborn screening (NBS). Methods: After brief genetics orientation, parents rated their interest in receiving genomic testing for their healthy newborn on a 5-point Likert scale and answered questions about demographics and health history. We used logistic regression to explore factors associated with interest in genomic testing and tracked any subsequent rejection of NBS. Results: We queried 514 parents within 48 hours after birth while still in the hospital (mean age (sd) 32.7 (6.4) years, 65.2% female, 61.2% white, 79.3% married). Parents reported being not at all (6.4%), a little (10.9%), somewhat (36.6%), very (28.0%) or extremely (18.1%) interested in genomic testing for their newborns. None refused conventional NBS. Married participants and those with health concerns about their infant were less interested in newborn genomic testing (p=0.012 and p=0.030, respectively). Mothers’ and fathers’ degree of interest was discordant (≥ 2 categories different) in 24.4% of couples. Conclusions: Interest in newborn genomic testing was high among parents of healthy newborns and the majority of couples had similar levels of interest. Surveying parents about genomic sequencing did not prompt rejection of NBS