PMSF initiated the Phelan-McPosium to bring families affected by PMS, clinicians, and researchers together to design patient-centered rigorous clinical and translational research. Here, we present findings from the 2018 Phelan-McPosium which was attended by 183 families and 35 researchers and clinicians. Overall, the Early Childhood parents raised the fewest number of concerns, families of Late-Childhood patients raised more concerns around epilepsy and behavioral problems, and Teen and Adult families were primarily concerned about the implications of genetic testing, gastrointestinal dysfunction, and regression. All families were concerned with the feasibility, safety, and importance of clinical trials for PMS.