Dominant males of many of the mouthbrooding Gymnogeophagus (labiatus, tiriparae, mekinos, pseudolabiatus, etc.) get a bug hump.
The key thing with all of these fish from Uruguay/temperate Argentina & Brazil is giving them a cool-down in the winter. If they don't get it, they'll look great for a year or so... and then succumb to all sorts of maladies.