What is 22q11.2 Duplication Syndrome?
22q11.2 duplication is a condition where there is an extra copy of a small piece of chromosome 22. This condition can cause features that vary widely amongst individuals, even members of the same family. Many people with 22q11.2 duplication have no apparent physical or intellectual disabilities. Others do exhibit features. 22q11.2 duplication occurs from a baby’s conception.
22q11.2 duplication syndrome is also known as Chromosome 22q11.2 microduplication syndrome.
Approximately 70% of duplication cases are inherited from a parent, whereas others have a new genetic occurrence (de novo). If a person with 22q duplication has a child, there is a 50% chance of passing on the condition.
It is believed that it occurs 1:4,000 pregnancies, however this is expected to be higher as many cases go undiagnosed due to the variance in symptoms therefore the true number of cases is unknown.
22q duplications are not detectable by karyotyping (an older method of genetic testing). Most individuals with 22q11.2 duplication are identified either by array genomic hybridization (array GH) testing or multiplex ligation-dependent probe amplification (MLPA) testing. Both tests are performed on blood samples.
22q duplications can also be diagnosed in pregnancy using cells from the placenta or the amniotic fluid.
22q duplication symptoms vary amongst individuals. Symptoms can range from none to mild, moderate or occasionally severe.
There is a wide variability in the types and severity of associated symptoms, including birth defects, medical problems, and developmental differences. 22q11.2 duplication can also result in very mild symptoms or none at all.