| Trisomy 9 | |
|---|---|
 | |
| Chromosome 9 | |
| Specialty | Medical genetics  |
| Causes | three copies of Chromosome 9 |
| Prognosis | Invariably fatal, no known effective treatment |
Full trisomy 9 is a rare and fatal chromosomal disorder caused by having three copies (trisomy) of chromosome number 9. It can be a viable condition if the trisomic component affects only part of the cells of the body (mosaicism) or in cases of partial trisomy of the short arm (trisomy 9p) in which cells have a normal set of two entire chromosomes 9 plus part of a third copy of the short arm ("p") of the chromosome.