What disorder results from a translocation between chromosome 18 and 21 or between 19 and 21?
Although I was able to find several references to case reports involving both 18/21 and 19/21 translocations, neither of these is responsible for a specific genetic syndrome. Down’s syndrome is trisomy 21 (three copies), and this did occur in one of the case reports of an 18/21 translocation, but it sounds like the patient had some pretty bizarre chormosomal abnormalities all at the same time. I suspect that all of them hark back to some root cause common to all of them, such as global damage to mom’s ova or dad’s spermatocytes. The classic and well described chromosomal translocation with a clinical phenomenon attached is a 9/22 translocation that creates the bcr-abl fusion oncogene. 9/22 translocation is called “philadelphia chromosome” and it is the cause of a type of leukemia.
