Diseases that Sound Horrible But Aren't

Alopecia: baldness

Paruresis: Inhibited urination, especially in the presence of strangers, i.e. the shy kidneys

Now that I think about it, any time you give something a hefty Greek-derived name, it makes it sound worse. Although "poliosis" sounds like it could either be related to polio or scoliosis, neither of which sound like much fun.