# Navigating adulthood with PKU: metabolic outcomes, quality of life, and mental health 4.5 years post-transition

## TL;DR

This study examines how adults with PKU manage their condition after transitioning to adult care, finding that psychiatric issues are linked to worse outcomes.

## Contribution

The study highlights the importance of integrating psychological support into adult PKU care to improve adherence and outcomes.

## Key findings

- Structured transition into adult care supports metabolic stability and adherence in PKU patients.
- Psychiatric comorbidities are strongly linked to higher phenylalanine levels and lower quality of life.
- Consistent amino acid mixture use and low-protein diet adherence are associated with lower phenylalanine concentrations.

## Abstract

Adult care for individuals with phenylketonuria (PKU) remains limited, as many centers prioritize pediatric patients. Structured transition into adult care is essential to maintain metabolic stability, adherence, and monitor comorbidities - particularly psychiatric ones. This study evaluates metabolic control, quality of life (QoL), and the impact of psychiatric comorbidities in adults with PKU after transition.

This retrospective study included 45 adults with PKU assessed 4.5 years after entering adult care. Data from transition and annual follow-ups were analyzed. Phenylalanine (Phe) concentrations were assessed using venous blood samples and dried blood spots. Dietary habits and amino acid mixtures (AAM) intake were recorded via interviews. QoL was measured with the PKU-QOL (0-100; lower scores indicate better QoL) and WHO-5 (0–25, higher scores indicate better well-being). Comorbidities were obtained from medical records.

Mean Phe concentration remained stable (998.3 ± 290.4µmol/l). Adherence to low-protein diet increased from 77.8% to 100%, and AAM intake from 62.5% to 85.8% over 4.5 years. Consistent AAM use (≥ 3x/day) and adherence to low-protein diet were each associated with lower Phe levels compared to no AAM or no diet (− 362.9µmol/l and − 304.1µmol/l, p < 0.05). Overall, 89% had comorbidities, most commonly psychiatric disorders (31%). These individuals showed higher Phe levels (1169µmol/l vs. 823µmol/l, p < 0.05), lower dietary adherence (33% vs. 70%, p < 0.01), and greater QoL impairment.

Structured transition into adult care supports metabolic stability. However, psychiatric comorbidities are strongly linked to poorer adherence and worse metabolic and psychosocial outcomes. Integrating psychological support into adult PKU care is therefore essential.

A structured transition into adult care can support the maintenance of metabolic control and quality of life in adults with PKU, especially given the high prevalence of psychiatric comorbidities, which can negatively affect adherence.

The online version contains supplementary material available at 10.1186/s13023-025-04186-1.