The Phelan-McDermid syndrome community has experienced profound grief and concern over the deaths of some of our beloved children and adults. The Phelan-McDermid Syndrome Foundation (PMSF) is urgently working with the PMSF Medical Advisory Committee (MAC) to understand the causes of these deaths and has begun a “mortality review.” This review is a comprehensive and detailed process of speaking with families, reviewing medical records in depth, and identifying causes of death and any patterns that emerge which will be helpful to reduce risk.