Bugs that cause bizarre behaviour

"Sammy Maloney was a healthy, outgoing 12-year-old, who played in the school band, and liked nothing better than to dump his backpack after school and hang out with his friends in Kennebunkport, Maine. Then, in 2002, Sammy's personality began to change. "The first thing I noticed was that he was walking around the backyard with his eyes closed," says Sammy's mother, Beth Maloney. "I asked him what he was doing, and he said he was memorising."

The next day, Sammy was again walking with his eyes closed and would only use the back door. Then he progressed to holding his breath while doing it, only wearing certain coloured clothes, and refusing to allow the windows to be opened, or the lights to be switched off.
Sammy was diagnosed with obsessive compulsive disorder, and then Tourette's syndrome. When he continued to deteriorate, a friend suggested testing Sammy for streptococcus - a common childhood bacterial infection that usually causes no more than a sore throat.
Sammy hadn't shown any signs of streptococcal infection, but it turned out he was infected. When doctors prescribed antibiotics, his symptoms began to improve. Within a few weeks he was playing board games with his brothers. "After six months of treatment, I knew that he would recover," says Beth."
via New Scientist/read more