Maybe. Or maybe it's something that varies how it manifests from person to person. For example, EDS is a connective tissue disorder, but there are 13 distinct types of it and doctors almost never check for it. Yet 1 in 5000 people in the world have it.

Endo is another one. Astounding how uterine tissue growing on one's organs can mess up how one functions. When I had growths on my spine, I used to pass out with no warning. Just 1, 2, 3 floor.