What is The Phelan-McDermid Syndrome?
“Don’t worry,” my then first grade daughter re-assures her friend. “You can’t catch it.” Together they stare at her two year old brother as he scoots down the stairs on his diapered butt towards them squealing with glee. His ears are over-large, his chin a bit pointed, and his smile raises his pale puffy cheeks so that he resembles a cherub cloaked in joy.
What is The Phelan-McDermid Syndrome
The Phelan-McDermid Syndrome, is a genetic condition which meant a piece on chromosome 22, long arm (q), region 1, band three, sub-band three did not exist or had been compromised. Our child was the thirty-fourth in the world to receive this diagnosis in 1998. Today there are about four hundred individuals in the world with this chromosome deletion. The condition is named for Dr. Katy Phelan and Dr. Heather McDermid who first identified the condition. Dr. Katy Phelan brought the original first fifteen families together into what is now The Phelan-McDermid Syndrome Foundation. In 2008, over 100 families attended the support group’s bi-annual conference on the East Coast.
Diagnosing The Phelan-McDermid Syndrome:
The chromosome deletion is often difficult to see by routine chromosome studies, therefore, a special test called FISH (fluorescence in situ hybridization) is often used. In FISH studies, a DNA probe that is specific for the tip of the long arm of Chromosome 22 is used to see if the 22q13 segment is present or absent. If your child has Phelan-McDermid Syndrome, the 22q13 region will be present on the normal chromosome but absent on the deleted chromosome. A more recently developed technique, micro-array comparative genomic hybridization (CGH), is also used to identify the loss or gain of chromosome material. It is more sensitive than FISH in detecting loss of very small regions of the chromosome and can examine all of the chromosomes at once, rather than targeting only chromosome 22. The deletion can also be detected in cells from skin or in cells obtained for prenatal diagnostic testing.
Most Common Characteristics
Some of the most common characteristics include: Ptosis (droopy eyelid), a pointed chin, prominent poorly formed ears, puffy hands,thin flaky toenails, wide nasal bridge, hypotonia (poor muscle tone), tendency to oveheat, and lack of perspiration. Behavioral characteristics include chewing on non food items (clothing, bedding, toys) – teeth grinding, tongue thrusting, hair pulling, aversion to clothes, decreased perception of pain and anxiety in social situations. Many children fall somewhere in the autism spectrum. Some medical issues include seizures, chronic diarrhea, macrocephaly, reactive airway disease (asthma). Very few of the children have speech or toilet training skills.