A couple of medical conditions I have heard about recently. Up to you to research how common they are and the rest:-

macular degeneration - partial blindness in your eye/eyes. Genetically linked but recessive so you need gene from both parents but they don't necessarily have the condition. I think there's different versions that can effect you from birth or middle age.

There's a condition, don't know the name of it, where people are hypersensitive to certain textures. It's not autism. My nephew wouldn't eat anything soft including fruit or even icecream! He also wouldn't touch playdoh. In past generations they wouldn't call this a condition just being fussy!