Hi Susan, I work at the National Organization for Rare Disorders (NORD) and our genetic counselor on staff shared that incidence and prevalence data for rare chromosome abnormalities is usually not available and many diagnoses are completely unique. The best resources for information and support for rare chromosome abnormalities are the following:
http://www.chromodisorder.org and
http://www.rarechormo.org. Please feel free to contact us if you have any other questions. -Tai