Microdeletions – result in a very small piece of chromosome to be missing. Special tests are needed to detect these. Many of these entities are variable (i.e. every person’s are a bit different).
Incidence 1/2000-4000
Presents in many ways:
In newborn period – digeorge syndrome, immune problems, heart problems.
In adolescent period – speech problems, learning disabilities, social problems, hyper-nasal speech.
In adult period – behavioral problems, psychological problems.
10-25% familial origin, but almost always (75%) from mother. This may be because women with this condition can more often form stable relationships resulting in children.
Microdeletion is on chromosome 22, a gene rich chromosome. Is this deletion of one gene or many genes? Not known as of yet.