I have a female character, about 20 years old, who was adopted in a closed adoption. Her biological mother now has a son. He’s likely in his teens but may be younger. I’m not really sure yet if it matters unless it affects the answer to this question.
The biological mother discovers that her son has some sort of disease that is carried by women but only affects men. The biological mother then seeks out seeks out my character. Bio mom didn’t know if the adopted child was a boy or a girl and wanted to let the child know that either she could be a carrier or he could be affected, depending on gender, of course.
Ideally, I’d like something that is sufficiently serious [not like… color blindness] to warrant seeking out the adopted child, but not deadly in childhood especially but also prefer it to be something that could go unnoticed until adulthood and then managed, even if not cured.
Does that make sense? Is there anything that fits the bill?
I sat down with a doctor friend and we came up with two possibilities of X-linked disorders that would present later in life but are fairly serious enough to warrent a biological parent hunting them down.
1. McLeod Syndrome (this might be your best option).
2. XMEN Disease
XMEN Disease might take a while to diagnose and put you closer into the time frame of your question. It might be discovered after the child presents with frequent infections.