I have seen where some have suggested that he has the same thing that Abe Lincoln was suppose to have. I can't remember the name of it but one of the visible symptoms is the eyes seeming to look in different directions and being very tall and thin. It has something to do with your muscles if IIRC.
Pete Maravich had it. It's speculated Lincoln suffered from it, too. Kerry certainly looks like the type. Long, thin, bony, fingers, a weakened aorta, unusually tall and slender, almost droopy.
When a person whose extended arm span is longer than their height, the disease is suspected.