1. Epispadias, (or Vaginal Penis Disorder)
It is inarguable that the manliest thing about a man is exactly that which makes him a man: his penis. Conversely, what makes a woman feminine is her vagina (and the ability to make .75 cents for every dollar penises bring in). Now imagine waking up one day with a vagina-like opening in your penis. But don't be afraid; according to this random website (because hey, who would make up something this irrelevant), the problem is completely aesthetic, citing the only potential problem being a "lack of [bladder] control due to hypospadias can lead to acute social embarrassment," basically referring to the fact that you have to sit down when you pee due to your unique penis/vagina combination, making you the male equivalent of Rosie O'Donald. However, unlike a Hermaphrodite/Rosie O'Donald, you can't fulfill everyone's fantasy of taking their own virginity, so instead you simply have an emasculating condition which may technically make every woman you sleep with a lesbian. Which is sort-of hot, actually.
2. Irritable Bowell Syndrome (or Shit Yourself Syndrome)
For anyone who has literally had the "shit scarred out of them," this disorder is probably the reason why, although it's more likely that you're just a big pussy (see above disorder). Not to be outdone by other, more famous diseases such as AIDS and Cancer, IBS even has its own month, "IBS Awareness Month," which is April, apparently because it's the only month that had not yet been declared as a "month" by some other hilarious disease (see above disorder). It affects women, mostly, so I can only imagine that the disorder was first diagnosed after the sexual experience behind your sister's nickname "Ass-Pussy." Or, if you're Camille Grammer, wife Kelsey Grammer (from Frasier, Cheers and...uhm...that's about it), it could be simply be being married to Kelsey Grammer.
It's basically the equivalent of Celine Dion marrying Al Franken...which would look something like this:
3. Lactose Intolerance (it even has its own Website: http://www.lactose.com.au/)
I'll get back to you later b/c apparently I've been on the computer for 36 hours...I wonder if that counts?
4. Internet Addiction Disorder (IAD) http://www.themedguru.com/articles/internet_addiction_a_clinical_disorder-86116769.html