Everything posted by John S
Here's a report on an adult female who was homozygous for hemophilia: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3385172/. She suffered from the condition as expected, but it was not lethal. And here's the abstract of another report of a homozygous adult female who had the condition but for whom it was not lethal: https://www.karger.com/Article/PDF/208614.
People can survive with multiple copies of the X chromosome, although they usually have delayed cognitive development and reproductive abnormalities, among other symptoms. The larger the number of extra copies of the chromosome there are, the more severe the symptoms are. There have been cases of males born with as many as five copies of the X chromosome. In this case, their karyotype would be 50, XXXXXY.