Question: How many people are affected by 9q22.3 microdeletion ?
Answer: 9q22.3 microdeletion appears to be a rare chromosomal change. About three dozen affected individuals have been reported in the medical literature.
Source: GHR

Question: What are the genetic changes related to 9q22.3 microdeletion ?
Answer: People with a 9q22.3 microdeletion are missing a sequence of at least 352,000 DNA building blocks (base pairs), also written as 352 kilobases (kb), in the q22.3 region of chromosome 9. This 352-kb segment is known as the minimum critical region because it is the smallest deletion that has been found to cause the signs and symptoms described above. 9q22.3 microdeletions can also be much larger; the largest reported deletion includes 20.5 million base pairs (20.5 Mb). 9q22.3 microdeletion affects one of the two copies of chromosome 9 in each cell. People with a 9q22.3 microdeletion are missing from two to more than 270 genes on chromosome 9. All known 9q22.3 microdeletions include the PTCH1 gene. The protein produced from this gene, patched-1, acts as a tumor suppressor, which means it keeps cells from growing and dividing (proliferating) too rapidly or in an uncontrolled way. Researchers believe that many of the features associated with 9q22.3 microdeletions, particularly the signs and symptoms of Gorlin syndrome, result from a loss of the PTCH1 gene. When this gene is missing, patched-1 is not available to suppress cell proliferation. As a result, cells divide uncontrollably to form the tumors that are characteristic of Gorlin syndrome. Other signs and symptoms related to 9q22.3 microdeletions probably result from the loss of additional genes in the q22.3 region. Researchers are working to determine which missing genes contribute to the other features associated with the deletion.
Source: GHR