Impact of the COVID-19 Era on Phenylalanine Levels and Classical Phenylketonuria Patients Follow-Up: A Retrospective Analysis

Objective: Phenylketonuria is a metabolic disorder resulting from mutations in the PAH gene, causing elevated blood phenylalanine (Phe) levels which can lead to severe neurological damage if untreated. The primary treatment is a lifelong low-protein diet with amino acid substitutes and micronutrient supplements. During the COVID-19 pandemic, classical phenylketonuria (PKU) patients faced significant challenges, including restricted access to routine care like clinical visits and metabolic control monitoring. The aim of the this study was to examine the disruptions in outpatient visits, the variances in pre- and post-pandemic Phe levels, and clinical severity among patients who contracted COVID-19. Material and Methods: Starting from the pandemic date of March 11, 2020, demographic data, laboratory characteristics, and details about COVID-19 infection were retrospectively reviewed for classical PKU patients with accessible electronic records from March 2018 to March 2022. Results: When the median blood Phe levels before and after the pandemic were compared, a significant difference was found. We observed that adult patients diagnosed with classical PKU often defaulted on their follow-up appointments. Conclusion: The COVID-19 pandemic significantly disrupted the follow-up and management of classical PKU patients. However, no severe COVID-19 cases were reported among this population, suggesting they did not face an increased risk from the infection. This study emphasizes the critical need to develop robust strategies for patient engagement and follow-up, especially for adult classical PKU patients who are at risk of discontinuing routine care.