- Search the PWSA(USA) Web Site The Prader-Willi Syndrome Association was organized in the United States in 1975 to serve as an international vehicle of communication about Prader-Willi syndrome (PWS), a genetically based developmental disability. Now operating as PWSA (USA), this national membership association dedicated to Prader-Willi syndrome has as its stated mission: to provide to parents ...www.pwsausa.org