Impact of a Transition Clinic on Long-Term Care and Nutritional Management in Patients with Inborn Errors of Metabolism

<b>Background/Objectives</b>: The transition from pediatric to adult care in inborn errors of metabolism (IEM) is considered important to ensure continuity of care, adherence to treatment, and long-term metabolic control. However, transition processes are often delayed, and standardized protocols are lacking, which can negatively impact patient outcomes. This study aimed to evaluate the impact of structured transition consultations on adult care engagement, nutritional management, and follow-up adherence in patients with IEM. <b>Methods</b>: This retrospective study included 160 patients (59.4% women) diagnosed with IEM and with a mean age of 36.2 ± 11.6 years. Patients were divided into two groups: those who underwent a structured transition consultation (<i>n</i> = 41) and those who did not (<i>n</i> = 119). Data on demographic and clinical characteristics, dietary management, and follow-up adherence were collected. <b>Results</b>: Patients who underwent structured transition consultations were significantly younger at diagnosis (1 [IQR 131] months vs. 66 [IQR 359] months, <i>p</i> = 0.001) and at their first adult visit (24.4 ± 9.5 vs. 32.3 ± 10.6 years, <i>p</i> < 0.001) compared to those who did not. Neonatal screening (45% of the overall cohort) was more common among these patients (65.9% vs. 37.8%, <i>p</i> = 0.007) suggesting a trend toward smoother integration into adult care. The absence of dietary records was considerably more frequent in the non-transition group (43.7% vs. 17.1%), with a significant crude association (<i>p</i> = 0.007) that was attenuated after age adjustment (<i>p</i> = 0.064). Overall follow-up adherence was high (88.1%) and comparable between groups. <b>Conclusions</b>: Structured transition consultations in patients with IEM were associated with earlier participation in adult care, better maintenance of dietary records, and high overall follow-up adherence, even among younger patients typically at higher risk of disengagement.