So I am writing my own creepypasta/horror story and I need help creating or finding a disease that you are born with and kills you slowly (when i mean slowly i mean over 10 years slowly), that doctors (at least in 1987) couldn't recognize or treat.
Might be a bit too specific honestly. You could try just basing it off an existing illness and modifying it into an alternate strain so its easier to sustain plausibility, like AIDs/HIV.