Evaluation of patients affected by inherited metabolic disorders (IMDs) in adult centres: a snapshot from the first multi-centre Italian survey from the Italian society for the study of hereditary metabolic diseases and newborn screening (SIMMESN) adult metabolic working group

Background The increasing survival of patients with inherited metabolic disorders (IMDs) has led to a growing adult population requiring specialized care. Adult Metabolic Medicine (AMM) is therefore an expanding field, yet its organization in Italy has not been systematically evaluated. This study aimed to assess the structure, resources, and unmet needs of Italian Centres managing adult IMD patients. A 50-item survey was developed by the Adult Metabolic Working Group and distributed to all Italian Adult Centres affiliated with SIMMESN (Italian Society of Metabolic Disease and NBS) or MetabERN (European Reference Network for Metabolic Disorders). The questionnaire collected data on centre characteristics, staffing, facilities, patient population, and transition from paediatric to adult care. The survey was active from April 2022 to April 2023. Data were analysed using descriptive statistics. Results Twenty Centres responded, reporting 2,175 adult IMD patients. Centres were heterogeneously distributed across Italy, with limited representation in southern regions. Most were university hospitals (65%), and only 20% were exclusively dedicated to IMDs. Although 95% conducted research and all were eligible for clinical trials, only 55% had an in-house metabolic laboratory, and 65% provided dedicated inpatient beds. Staffing was limited (mean two physicians per Centre), with inconsistent availability of dedicated nurses, dieticians, and psychologists. The most prevalent conditions were lysosomal storage disorders (38.5%), mitochondrial disorders (18.6%), and amino acid disorders (16%). Only 30% of Centres had a formalized transition program. Based on expected annual transitions, the adult IMD population is projected to increase by 13.45% annually, doubling in approximately 7.4 years. Conclusions Adult IMD services in Italy are rapidly expanding but remain heterogeneous and under-resourced. National standards, structured transition pathways, and dedicated AMM training programs are urgently needed to ensure sustainable and equitable care.