Speech & communication
Absent or significantly delayed speech is common. Many people communicate in other ways, and AAC can help.
Understanding PMS
What is Phelan-McDermid Syndrome?
Phelan-McDermid Syndrome (PMS) is a rare genetic condition linked to the 22q13 region of chromosome 22. Here's a clear, compassionate starting point — for families, carers and anyone who wants to understand.
The basics
A change in one small part of chromosome 22
Phelan-McDermid Syndrome is usually caused by the loss (deletion) of a small piece of chromosome 22 — at a location called 22q13.3 — or by a change in the SHANK3 gene found there. SHANK3 plays an important role in how brain cells connect and communicate.
Because the amount of genetic material involved can differ from person to person, PMS affects each individual differently. Two people with the same diagnosis can have very different strengths, needs and journeys.
PMS is rare and is believed to be underdiagnosed — which is exactly why a connected global community matters. Greater awareness means earlier answers for more families.
At a glance
- Also known as
- 22q13 deletion syndrome
- Key gene
- SHANK3 (22q13.3)
- Named after
- Katy Phelan & Heather McDermid
- Type
- Rare genetic condition
- Diagnosed by
- Genetic testing
Common characteristics
How PMS can show up
Characteristics vary widely — not everyone will experience all of these. Every person with PMS is unique, with their own personality and potential.
Low muscle tone
Hypotonia can affect early motor milestones such as sitting, standing and walking.
Developmental delay
Global developmental delay and intellectual disability of varying degrees.
Autism features
Autism spectrum characteristics are frequently seen and vary widely from person to person.
Sleep & behaviour
Sleep differences and individual behavioural profiles are often reported by families.
Medical needs
Some individuals have additional medical needs; regular, coordinated care is important.
This is general awareness information, not medical advice. It should never replace guidance from qualified healthcare professionals. For diagnosis, care and decisions, always consult specialists familiar with PMS and the current clinical guidelines.
22q13.3 — the region at the heart of PMS
Diagnosis
How PMS is identified
PMS is confirmed through genetic testing — most often a chromosomal microarray, and sometimes sequencing of the SHANK3 gene. A diagnosis can bring clarity, access to appropriate support, and a community of families who understand.
- Genetic testing gives families answers and direction
- Early support can help each person reach their potential
- A diagnosis connects you to specialists and to other families
Make a difference
Your support helps a family feel less alone.
Every contribution funds research, connects families to the right association, and raises the global voice of the Phelan-McDermid community.