@rugbygirl - Yes, that would be considered a congenital disease. For instance, I have congenital toxoplasmosis.
Have you ever heard it said that a pregnant woman should not change a litter box? We actually only had outdoor cats when I was a kid, so my mother must have been exposes to cat feces while working in the garden or something like that. (In fact, cats that live exclusively indoors almost never get toxo, as cats generally pick it up from eating raw meat, as in critters that they hunt outside.)
She never even knew she was sick, but I have some minor eye problems that were first noticed when I was a teenager. I'm lucky, though - a lot of babies born with congenital toxoplasmosis are really, really sick.