22q13 Deletion Syndrome (spoken as twenty two q one three), also known as Phelan-McDermid Syndrome, is a genetic disorder caused by a microdeletion on chromosome 22. The deletion occurs at the terminal end of the chromosome at the location designated q13.3. This microdeletion is rarely uncovered by typical genetic screening, therefore a fluorescence in situ hybridization, or FISH, test is recommended to confirm the diagnosis. Recent work indicates Phelan-McDermid Syndrome may also be caused by errors in a single gene (SHANK3/PROSAP2) in the q13.3 region. Errors on the same gene have been associated with Autism Spectrum Disorder (ASD).
This genetic disorder is characterized by general hypotonia, absent to delayed speech, and global developmental delays. It is estimated that fewer than 500 people have been diagnosed with this syndrome, though this is only an estimate.
Individuals with a 22q13 deletion can suffer from a range of symptoms, with mild to very serious physical and behavioral characteristics. Possible symptoms are:
Physical
- Absent to severely delayed speech: 99%
- Hypotonia (poor muscle tone): 97%
- Normal to accelerated growth: 95%
- Increased tolerance to pain: 86%
- Thin, flaky toenails: 78%
- Large, fleshy hands: 68%
- Prominent, poorly formed ears: 65%
- Pointed chin: 62%
- Dolichocephaly (elongated head): 57%
- Ptosis (eyelid) (droopy eyelids): 57%
- Poor thermoregulation: 51%
Behavioral
- Chewing on non food items (clothing, bedding, toys):70%
- Teeth grinding: (percent undetermined)
- Autistic behaviors: (percent undetermined)
- Tongue thrusting: (percent undetermined)
- Hair pulling: (percent undetermined)
- Aversion to clothes: (percent undetermined)
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