He's the only persons doctors know of to ever have this condition.
ABC News: Meet the Boy Too Big for His Mom's SUV
Chromosomes, you may remember, come in pairs. But in Brenden's case, his 12th chromosomes don't match. Somehow -- experts still don't know why -- the middle of one of them broke off, flipped around and re-attached, disrupting a critical gene that controls growth. And that's what experts believe is causing Brenden's excessive growth and other symptoms and what makes his case the only one of its kind