BACKGROUND: Phelan-McDermid syndrome (PMS) is a rare neurodevelopmental disorder caused by deletions in chromosome 22q13.3 or pathogenic variants in the SHANK3 gene. Individuals present with intellectual disability, autism-spectrum traits, seizures, gastrointestinal and motor issues, and sleep disturbances, requiring lifelong multidisciplinary care. In Italy, PMS care is fragmented and unevenly distributed, with families often providing intensive home-based support at high personal, financial, and social costs. METHODS: This national participatory Citizen-Science study, conducted with the Italian Phelan-McDermid Syndrome Association (AISPHEM), will engage informal caregivers of individuals with genetically confirmed PMS across Italy. A qualitative phase using semi-structured online interviews will explore caregiving experiences, unmet needs, barriers to care, coping strategies, and social isolation. Insights will guide the creation of the first Italian PMS registry, capturing longitudinal clinical, socio-demographic, and caregiver-related data. EXPECTED RESULTS & CONCLUSIONS: The project will generate novel evidence on caregiver needs, develop the first national PMS registry, and produce a service map to support equitable, coordinated PMS care and a stronger national caregiver network in Italy.