Press Release: Landmark Autism Research Finds Phelan-McDermid Syndrome May Affect 1 in 7,300 People
Thousands of individuals with the condition are likely undiagnosed.
Study identifies underutilization of genetic testing as a major contributor to missed diagnoses.
Findings underscore the growing importance of genetic testing as precision therapies advance toward patients.
New York, NY (July 9, 2026) — New research, led by scientists from the Seaver Autism Center for Research and Treatment at Mount Sinai and published June 28 in Autism Research, has estimated that Phelan-McDermid syndrome (PMS) affects approximately 1 in 7,300 people, making it dramatically more common than previous estimates suggested.
Phelan-McDermid syndrome is a rare genetic condition caused by deletion or mutation of the SHANK3 gene on chromosome 22. The syndrome can cause a wide range of medical, intellectual, and behavioral challenges. The majority of patients with the syndrome also meet the criteria for autism spectrum disorder, and SHANK3 deletions or mutations are thought to account for up to one percent of autism spectrum disorder cases.
In collaboration with genetic testing laboratories, academic medical centers, and autism research programs, Mount Sinai researchers analyzed data from nearly 180,000 individuals with autism who underwent genetic testing. They combined data from ten independent sources, including GeneDx, Labcorp, Ambry Genetics, the SPARK research study, the Autism Sequencing Consortium, and several leading children's hospitals.
After adjusting for undiagnosed cases, testing limitations, and individuals with Phelan-McDermid syndrome who do not meet criteria for autism, investigators estimated a prevalence of 13.7 cases per 100,000 people, equivalent to about 1 in 7,300 individuals. The new findings represent a dramatic shift from previous estimates and indicate that more than 45,000 people in the United States may be living with the condition.
"The large gap between known and estimated cases is likely due in large part to the fact that many individuals with developmental disabilities and autism are never offered genetic testing. Families may also face insurance barriers or may receive tests that do not adequately evaluate the SHANK3 gene," said Tess Levy, MSc, Assistant Professor of Psychiatry at the Icahn School of Medicine at Mount Sinai, a certified genetic counselor at the Seaver Autism Center, and first author of the paper.
"We recommend that every child with autism undergo genetic testing, because knowledge is power. These genetic findings allow researchers to design more targeted clinical trials for potential therapies. I truly believe that within the next five years, we'll see successful examples of new treatments coming from these genetic discoveries," said Joseph D. Buxbaum, PhD, Director of the Seaver Autism Center, co-founder of the Autism Sequencing Consortium, and senior author of the paper.
The study, supported by CureSHANK and Neuren Pharmaceuticals, represents one of the most comprehensive efforts ever undertaken to estimate the prevalence of Phelan-McDermid syndrome.
"Neuren Pharmaceuticals initiated this landmark PMS prevalence study in collaboration with the Seaver Autism Center at Mount Sinai and CureSHANK because, with new treatments moving closer to reality, identifying these individuals has become an ethical imperative. Patients cannot benefit from these advances if they never receive a diagnosis,” said Rachel Groth, PhD, Head of External Innovation and Patient Advocacy at Neuren Pharmaceuticals.
The publication arrives at a pivotal moment for the field. Multiple Phelan-McDermid syndrome clinical trials are underway, including precision medicine approaches designed to address the underlying biology of the disorder. For individuals and families affected by this condition, a genetic diagnosis is no longer simply an explanation. It is increasingly a gateway to specialized care, research opportunities, clinical trials, patient support communities, and potentially disease-modifying therapies.
"This study confirms what many families, clinicians, and advocates have suspected for years," said CureSHANK Board Chair, Geraldine Bliss. "There are likely tens of thousands of individuals with Phelan-McDermid syndrome who have never received a genetic diagnosis. At a time when multiple therapeutics are advancing into clinical trials, finding these individuals has never been more important."
The findings support the urgency behind CureSHANK's efforts to expand access to genetic testing and the broader goals of Start Genetic, a global awareness campaign launched to encourage patients, families, health care providers, and advocacy organizations to think genetic first. They also underscore a fundamental truth: patients cannot benefit from precision medicine if they are never diagnosed.
Read the full study in Autism Research: https://onlinelibrary.wiley.com/doi/10.1002/aur.70297
This project was funded by Neuren Pharmaceuticals, CureSHANK and Seaver Autism Center.
About CureSHANK
CureSHANK, a 501(c)(3) research advocacy organization, was founded in 2018 by three parents whose children live with Phelan-McDermid syndrome (PMS), a rare, highly disabling neurodevelopmental disorder currently without cure or FDA-approved therapies. Headquartered in Los Angeles, CA, CureSHANK's mission is to expedite life-changing therapies for people with PMS and other SHANK3-related disorders by bridging the translational research gap. To learn more, please visit www.cureshank.org.
About Neuren Pharmaceuticals
Neuren Pharmaceuticals is developing new drug therapies to treat multiple serious neurological disorders caused by genetic abnormalities or brain injury, that have no or limited approved treatment options. Neuren’s therapies target the critical role of Insulin-like growth factor 1 (IGF-1) in the brain, using orally administered analogs of naturally occurring peptides.
DAYBUE® (trofinetide) oral solution is approved by the US Food and Drug Administration (FDA), Health Canada and the Ministry of Health in Israel and DAYBUE STIX (trofinetide) powder is approved by the FDA for the treatment of Rett syndrome. Neuren has granted an exclusive worldwide license to Acadia Pharmaceuticals Inc. for the development and commercialisation of trofinetide.
Neuren’s second drug candidate, NNZ-2591, is in clinical development as an oral solution treatment for multiple neurodevelopmental disorders, with positive results achieved in Phase 2 clinical trials in Phelan-McDermid syndrome, Pitt Hopkins syndrome and Angelman syndrome. Each of these programs has been granted “orphan drug” designation in the United States and the European Union as well as Fast Track and Rare Pediatric Disease designations from the FDA. Neuren is also developing NNZ-2591 for the treatment of hypoxic ischemic encephalopathy (HIE), a serious condition caused by brain injury before or shortly after birth.
Currently, Neuren is conducting a Phase 3, randomized, double-blind, placebo-controlled clinical trial (“Koala”) evaluating the safety and efficacy of NNZ-2591 in children aged 3 to 12 years with Phelan-McDermid syndrome and a 52-week open-label extension study. To learn more, please visit www.neurenpharma.com
About the Icahn School of Medicine at Mount Sinai
The Icahn School of Medicine at Mount Sinai is internationally renowned for its outstanding research, educational, and clinical care programs. It is the sole academic partner for the seven member hospitals* of the Mount Sinai Health System, one of the largest academic health systems in the United States, providing care to New York City's large and diverse patient population.
The Icahn School of Medicine at Mount Sinai offers highly competitive MD, PhD, MD-PhD, and master's degree programs, with enrollment of more than 1,200 students. It has the largest graduate medical education program in the country, with more than 2,700 clinical residents and fellows training throughout the Health System. The Graduate School of Biomedical Sciences offers 12 degree-granting programs, conducts innovative basic and translational research, and trains more than 470 postdoctoral research fellows.
Ranked 11th nationwide in National Institutes of Health (NIH) funding, the Icahn School of Medicine at Mount Sinai is among the 90th percentile of U.S. private medical schools in Sponsored Programs Direct Expenditures per Principal Investigator, according to the Association of American Medical Colleges. More than 6,900 scientists, educators, and clinicians work within and across dozens of academic departments and multidisciplinary institutes with an emphasis on translational research and therapeutics. Through Mount Sinai Innovation Partners (MSIP), the Health System facilitates the real-world application and commercialization of medical breakthroughs made at Mount Sinai.
