Brazilian Patients With Phenylketonuria: Neuropsychological Profile, Correlation With Metabolic Measurements, and the Importance of Treatment Adherence

Objective: Phenylketonuria (PKU) is characterized by a deficiency in phenylalanine hydroxylase, a key enzyme responsible for the metabolism of phenylalanine (Phe). Neuropsychological alterations have been observed in individuals treated for PKU, including decreases in intelligence quotient (IQ) and processing speed impairments. However, studies demonstrating a correlation between phenylalanine variation and neuropsychological changes are scarce and present conflicting results. Additionally, treatment adherence is seen as one of the most important aspects of Phe control. Therefore, this study aimed to clarify the cognitive performance of Brazilian children with PKU by comparing it with normative data from intelligence-evaluating tests and examining the association with Phe levels throughout several stages of childhood development. Additionally, this work provides a perspective on treatment adherence and data from a Brazilian pediatric population. Method: Twenty participants aged 6-11 years of age who were treated for PKU or hyperphenylalaninemia participated in the study. The Wechsler Intelligence Scale for Children-Fourth Edition was used to measure IQ, and metabolic measurements included all Phe measurements that were collected from birth until the project was conducted. Results: There was no reduction in Phe levels over this period of sampled time. In addition, negative Bayesian correlations were found between the Phe variation and processing speed, but not with total IQ. Conclusions: The investigation of Phe variation and its relationship with cognitive abilities and possible methods of care for patients with this condition is essential in improving our understanding of patient profiles and ensuring better care. Public Significance Statement This study has a Brazilian sample and presents the reality of Brazilian people with phenylketonuria. The data collected has imminent implications for health professionals of Brazil who are working in populations with phenylketonuria, thus a Journal that publishes scientific articles to health professionals of Brazil is the best option.