Quality of life after diet liberalization in individuals with phenylketonuria treated with Pegvaliase

Objective To assess the impact of pegvaliase treatment on quality of life and individuals' perception of and satisfaction with therapy in Italian individuals with classical phenylketonuria (PKU) after diet liberalization. Methods This longitudinal observational study included individuals with classical PKU and persistently poor dietary adherence who initiated treatment with pegvaliase and achieved diet liberalization. Blood Phe levels were measured at baseline and throughout treatment for up to 12 months following diet liberalization. Quality of life was assessed using the Phenylketonuria–Quality of Life (PKU-QOL) questionnaire at three time points (before treatment, and 6 and 12 months after diet liberalization); a qualitative satisfaction survey was also administered. Results Seven participants (1 male, 6 females; mean age 27.7 years) achieved diet liberalization within a mean of 61 weeks after maintenance period, with a mean reduction in blood Phe levels of 79.7%. At 6 and 12 months after diet liberalization, PKU-QOL scores showed a consistent decrease, indicating improved quality of life, particularly in the “PKU in general” subscale, assessing the emotional, practical, and social impact of PKU. Patient-reported outcomes highlighted improvements in energy levels, sleep quality, emotional well-being, and social functioning. Common challenges included injection-site discomfort and initial treatment-related anxiety. Conclusions Pegvaliase treatment was effective in reducing blood Phe levels and achieving diet liberalization, thereby improving quality of life in individuals with PKU who historically had poor dietary adherence. Despite initial treatment challenges, the therapy enabled substantial improvements in quality of life and dietary freedom.