Overview
Phelan-McDermid syndrome (also called 22q13.3 deletion syndrome or PMS) is a rare genetic condition caused by a missing piece at the end of chromosome 22. This missing piece affects how the brain and body develop, leading to a wide range of challenges that vary from person to person. The condition is named after the researchers who first described it in detail. The most common features include moderate to severe intellectual disability, absent or very limited speech, low muscle tone (called hypotonia), and autism-like behaviors. Many people with Phelan-McDermid syndrome have delayed milestones like sitting, walking, and talking. Some individuals never develop spoken language. Other features can include minor physical differences, a reduced sensitivity to pain, and a tendency to chew on non-food items. There is currently no cure for Phelan-McDermid syndrome. Treatment focuses on managing symptoms and supporting development. This includes speech therapy, occupational therapy, physical therapy, and special education programs. Some medications are used to manage seizures or behavioral challenges. Research into targeted treatments, including studies on insulin-like growth factor 1 (IGF-1) and other therapies, is ongoing and offers hope for the future.
Key symptoms:
Intellectual disability, usually moderate to severeAbsent or very limited speechLow muscle tone (hypotonia)Autism-like behaviors such as repetitive movements or difficulty with social interactionDelayed milestones like sitting, walking, and talkingReduced sensitivity to pain or heatTendency to chew on clothing or non-food objectsSeizures in some individualsSleep disturbancesMinor physical features such as large or fleshy handsThin or dysplastic toenailsGastroesophageal reflux or feeding difficultiesBehavioral changes or regression, especially in adolescence or adulthood
Clinical phenotype terms (50)— hover any for plain English
Sporadic
Usually appears on its own, not inherited from a parent
Neonatal
Begins at or shortly after birth (first 4 weeks)
FDA & Trial Timeline
4 eventsNeuren Pharmaceuticals Limited — PHASE3
Peking University First Hospital — NA
Jaguar Gene Therapy, LLC — PHASE1, PHASE2
Boston Children's Hospital
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Phelan-McDermid syndrome.
4 clinical trialsare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Phelan-McDermid syndrome.
Community
No community posts yet. Be the first to share your experience with Phelan-McDermid syndrome.
Start the conversation →Latest news about Phelan-McDermid syndrome
Disease timeline:
New recruiting trial: A Study of NNZ-2591 in Pediatric Participants With Phelan-McDermid Syndrome
A new clinical trial is recruiting patients for Phelan-McDermid syndrome
New recruiting trial: JAG201 Gene Therapy Study in Children & Adults With SHANK3 Haploinsufficiency
A new clinical trial is recruiting patients for Phelan-McDermid syndrome
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.What size is the deletion on chromosome 22, and which genes are affected beyond SHANK3?,Should other family members be tested, and what is the chance of this happening again in a future pregnancy?,What therapies should we start right away, and how often should they happen?,What signs of neurological regression should we watch for, and what should we do if we notice them?,Are there any clinical trials or research studies our child might be eligible for?,Does my child need kidney or heart screening, and how often?,What resources or support groups are available for our family?
Common questions about Phelan-McDermid syndrome
What is Phelan-McDermid syndrome?
Phelan-McDermid syndrome (also called 22q13.3 deletion syndrome or PMS) is a rare genetic condition caused by a missing piece at the end of chromosome 22. This missing piece affects how the brain and body develop, leading to a wide range of challenges that vary from person to person. The condition is named after the researchers who first described it in detail. The most common features include moderate to severe intellectual disability, absent or very limited speech, low muscle tone (called hypotonia), and autism-like behaviors. Many people with Phelan-McDermid syndrome have delayed milestone
How is Phelan-McDermid syndrome inherited?
Phelan-McDermid syndrome follows a sporadic inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Phelan-McDermid syndrome typically begin?
Typical onset of Phelan-McDermid syndrome is neonatal. Age of onset can vary across affected individuals.
Are there clinical trials for Phelan-McDermid syndrome?
Yes — 4 recruiting clinical trials are currently listed for Phelan-McDermid syndrome on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat Phelan-McDermid syndrome?
25 specialists and care centers treating Phelan-McDermid syndrome are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.