Scientists at Mount Sinai's Seaver Autism Center examined genetic data from nearly 180,000 autistic children to understand how many might actually have Phelan-McDermid syndrome (PMS), a condition caused by a missing or faulty gene called SHANK3 on chromosome 22. The study, published in Autism Research, asked: how many people with this genetic condition have been missed or misdiagnosed?
Most children with PMS also meet the criteria for autism spectrum disorder. The researchers wanted to know the true prevalence by combining information from ten separate sources, including major genetic testing laboratories and children's hospitals across the United States.
The condition is likely five times more common than we thought
Previous estimates suggested PMS was extremely rare. This new analysis suggests approximately 1 in 7,300 people have the condition—meaning more than 45,000 Americans could be living with it undiagnosed. The jump in numbers reflects cases that are never tested, families who face insurance barriers, or children who received incomplete genetic screening.
Many autistic children may never receive genetic testing
The study highlights a significant gap: many children diagnosed with autism never undergo genetic testing to check for underlying conditions like PMS. Researchers emphasize this is not about doubting an autism diagnosis—it's about identifying whether a specific genetic cause exists. Understanding the genetic root matters because it can open doors to targeted treatments designed for that particular condition, rather than general autism interventions.
Genetic testing could reveal treatable causes
The research team believes that within five years, targeted therapies based on genetic discoveries like SHANK3 mutations may become available. Identifying PMS early matters because future treatments may address the root cause rather than managing symptoms alone. However, this is still emerging—no specific treatments for PMS are currently approved, though research is actively underway.
Next steps for your child's evaluation
- Ask your child's doctor whether genetic testing has been offered as part of their autism evaluation, especially if development delays appeared early.
- If genetic testing was done, check whether it specifically assessed the SHANK3 gene or used a comprehensive method that would catch deletions on chromosome 22.
- Keep records of any genetic test results; new findings emerge regularly, and older tests may need reanalysis with updated knowledge.