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Phelan-McDermid syndrome (pronounced FAY-luhn mick-DUR-mid) is a rare genetic disorder involving chromosome 22 that can affect many critical functions in a person’s body — from learning and communicating to eating and sleeping.

Children with this complex medical condition are born with a genetic difference on their 22nd chromosome that affects brain development and functioning. This results in intellectual and physical disabilities that vary from person to person. Some people with Phelan-McDermid syndrome lose essential skills, and most require long-term care and medical attention.

You may see and hear Phelan-McDermid syndrome abbreviated as PMS. You may also see Phelan-McDermid syndrome referred to as 22q13 deletion syndrome, based on the location of the genetic change in the body.