Study estimates Phelan-McDermid syndrome affects 1 in 7,300 people
A new analysis combining data from nearly 180,000 autistic individuals suggests Phelan-McDermid syndrome, caused by SHANK3 gene changes, occurs in about 13.7 per 100,000 people. The researchers warn that many cases remain undiagnosed because genetic testing is often skipped. The condition is linked to autism and may account for up to 1% of autism cases.
The study pooled data from roughly 180,000 autistic individuals across ten sources, including commercial laboratories, research consortia, and children's hospitals. After adjusting for undiagnosed cases, testing limitations, and individuals with PMS who do not meet autism criteria, researchers arrived at 13.7 cases per 100,000 people, translating to more than 45,000 Americans. The condition stems from SHANK3 gene alterations on chromosome 22 and may underlie up to one percent of autism cases.
Most people with PMS meet autism criteria, yet many never receive genetic testing due to insurance barriers or test panels that inadequately evaluate the SHANK3 gene. The authors advocate for universal genetic testing in autism, noting that identifying SHANK3 changes could accelerate targeted clinical trials. With treatments already moving toward trials, the researchers project meaningful therapeutic advances within five years.
This prevalence estimate could reshape how clinicians approach autism diagnosis, potentially prompting broader genetic screening recommendations. Families may gain access to earlier diagnoses and emerging targeted therapies, while researchers could see improved trial recruitment. However, expanded testing carries implications for healthcare costs and genetic counseling capacity. The findings may also influence how rare disease communities advocate for resources, though actual diagnostic rates depend on insurance policies and clinical practice changes over time.