Here are some diseases that are probably really horrible and I hope I never contract, but which nevertheless sound sort of quaint and amusing:

Shingles - Can anyone hear the name of this affliction without a mental image of a picturesque little disease-infested cottage, roof thatched with the advanced form of Chicken Pox? I sure can't.

Rickets - I have no idea what this is. It sounds like it has to do with two of my favorite things though: 1. Robots and B. frogs. Hence, Robot Frogs! or Frog Robots I guess would work too. I'll have to contact the FDA to see if any of the treatment for Rickets involves Robot Frogs.

The Gout - This one sounds like it should be said by a pirate. As in "Arr! Ye've got The Gout, Jim-Boy! Nothin a quick trip round the keel won't fix, though, eh me lubbin finey?" (Note: "Me lubbin finey" is not widely accepted as real pirate talk. Some of your more advanced pirates would try this sort of phrase, in hopes that it would catch on amongst their pirate colleagues, with little success. Every once in a while, a gem would crop up though, and a mellifluous turn of phrase like "newt-booty" would be born.)
(Note: previous note totally untrue. I just got carried away.)

Scurvy - Another pirate disease! Pirates seem a fun-loving bunch when you picture them lashing people to the mast, having feisty cutlass duels and counting their captive's teeth, all the while sucking on half a lime, which would protrude from their mouths, and give the impression that they had a green beak.