What happened to this man’s taste buds?

Remember geographic tongue, with its smooth red ‘islands’ in a sea of papillae?
Well, this patient’s condition was more like a continent.
The 64-year-old man’s entire tongue was erythematous, painful and totally bump-free — and had been for six months — when he presented to an oral medicine clinic in Singapore, also reporting a burning sensation around his lips.
But with a few laboratory tests, doctors had his symptoms licked.