Sex is a beautiful thing. It can also be difficult, terrifying or painful for some. Here are 10 such disorders that ruin sex for the people who have them.

10. Priapism

You know how at the tail end of Viagra commercials, after the previously limp man is happy and suggestively smiling with a woman, doing activities that aren't sex related at all, that voice comes on and quickly states some side effects along with the phrase "if you have an erection that lasts more than 4 hours, seek help?" Well, that's referring to priapism, a disorder that occurs when blood flows into the penis, but not out. It's considered a medical emergency, and can lead to erectile dysfunction, a disfigured penis and, in extreme cases, gangrene of the penis. We all know how gangrene is treated, right?

9. NREM arousal parasomnia

That's a fancy way of saying "sleep sex." People who suffer from sexsomnia engage in sexual activity while in the depths of REM sleep. It's terrifying on many fronts, especially considering the dubiousness of consent in that situation: both yours and that of your potential partner. Sexsomnia sufferers have been convicted of sexual assault, though sometimes their condition has also worked as a legal defense.

8. Persistent genital arousal disorder

Also known as PGAD, Weiss Disease or restless genital syndrome, persistent genital arousal disorder may sound fun for women, but it's actually a horribly inconvenient and damaging disorder. It was just recently identified in 2001, so not much is known about what causes it. It's most commonly found in people who have undergone hormone-therapy and menopausal women. A brief reprieve can be achieved through orgasm, but those genitals can become restless again as quickly as a few minutes.

7. Anorgasmia

Anorgasmia is a depressing disorder where people can't orgasm, no matter how much they're stimulated. It's more common in women than men, and not only is it annoying (think of a sneeze that never... arrives), it can lead to sexual frustration. One potential cause is the SSRI drugs used to treat depression.

6. Vaginismus

Also known as Vaginism, this disorder can be either psychological or physical, and refers to difficulty vagina-havers experience with penetration, be it sex or inserting tampons. What makes it difficult? The vagina muscles involuntarily clamp shut, making any acts of penetration painful or impossible. The best analogy for this disorder is that "the vaginismic reflex can be compared to the response of the eye shutting when an object comes towards it." It can also lead to "penis captivus," which I don't imagine I have to translate for you.

5. Retrograde ejaculation

Retrograde ejaculation is a common cause of infertility in men, and is the result of weakened bladder neck muscles. During male orgasm, these muscles constrict to prevent semen from going the wrong way. If these muscles are weak or damaged, it goes the wrong way, and only a dribble of semen (or none) ...goes out the front end.

4. Supernumerary sex organs

This one is pretty self explanatory, right? When someone's born with two penises, it's called Diphallia. Three or more testicles? Polyorchidism. Two uteri or vaginal canals? Uterus didelphys. An extra breast? That one doesn't have a cool name, it's just accessory breast. Also, don't google that; it's nothing like 'Total Recall.'

3. Postorgasmic illness syndrome

Another recently recognized disorder (2002), POIS is a depressing disorder characterized by "debilitating symptoms following orgasm that last for a few hours to several days." In case that didn't scare you enough, I'll just list the symptoms: cognitive dysfunction, intense discomfort, irritability, anxiety, susceptibility to illness, depression, difficulty communicating, remembering words, reading and retaining information, concentrating, and socializing, severe fatigue, mild to severe headache, flu and allergy-like symptoms (sneezing, itchy eyes, nasal irritation) and muscle pain.

2. Micropenis

A lot of men have anxiety about the size of their penises, but these are often unfounded (thanks porn). Some men, however, suffer from a disorder called "micropenis," which is exactly what it sounds like. Erect penises under 2.75 inches qualify for this classification, and there are a myriad of different causes. Sufferers often find penetration difficult to impossible, and for many years, doctors recommended sex reassignment surgery for children suffering from micropenis. Of course, since gender and sex are not the same thing, this led to some serious problems later in life.

1. Exclusive Paraphilias

Everybody has that one thing they fetishize that really gets them going, but it doesn't have to be there for them to enjoy sex. People who suffer from exclusive paraphilias only experience sexual arousal with the presence of what they fetishize, be it feet, children, full latex bondage (pictured) or car exhaust pipes.