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A major genetic analysis suggests Phelan-McDermid syndrome, a disorder closely linked to autism, may affect roughly 1 in 7,300 people, translating to more than 45,000 Americans — far higher than previous estimates. Researchers warn many cases likely go undiagnosed because genetic testing is not routinely performed. The findings come as targeted treatments for the condition move into clinical trials, raising the stakes for improved diagnosis to ensure more patients can access emerging therapies.