| Name | Short description | Estimated numbers |
| Klinefelter's Syndrome | When a child has an extra X chromosome in all cells (47,XXY) or in some cells (46,XY/47,XXY).For more information please visit the Klinefelter's Syndrome Association website. | 1/500-1/1000 men |
| Turner Syndrome | When a child has one X chromosome in all cells (45,X) or in some cells (45,X,46,XX).Other less common chromosome combinations are also possible. For more information please visit the Turner Syndrome Support Society website. |
1/2500 women
|
| 45.X/46,XY Gonadal Dysgenesis (sometimes called Mixed Gonadal Dysgenesis or Mosaicism) | Some cells in the body of a child with mixed dysgenesis (MGD) will contain 45 chromosomes, incl. a sinlge X, while other cells contain 46 chromosomes, incl, an X and a Y. Most children with MGD dvelop as typical boys and many will never know they have MGD. A small number will be born with internal and externa; reproductive and genital structures that are less typical. |
1/10 000 most develop as typical boys |
