Usually self mutilation is not so common in people that age.
I will skip the technical stuff, which is very much to the point, but focuses a lot on diagnosis.
The correct professional answer would be, first, to find out why you want to know the information. Curiosity about the sort of stuff is not general, and if you have curiosity it suggests that you actually know somebody who has this sort of issue. If you do know somebody with this sort of issue, you see, it'd be useful for you to get some sort of support yourself, because knowing somebody who does this sort of thing to themselves can be confusing and stressful, to say the least. The first concern a professional would have, you see, would be for you and how to make sure you got the support you need in dealing with this sort of behavior in somebody you know or care about.
Second, their concern would be to make it bluntly clear to you that this is their issue. Folks caught up in this sort of very painful life often tend to flail about them, and blame other people for their situation. In this, they can be a lot like folks with alcohol and drug problems. In fact, sometimes people who self mutilate also have drug and alcohol problems, though not always by any means.
This means that as far as teens go, it's sometimes useful to go to alateen or al-anon meetings, even if the person does not have a drug or alcohol problem, because some of the behavioral issues are the same and because Alateen and al-anon meetings are free. They try to teach you that you are powerless to control the behavior of the alcoholic, the drug addict or, in this case, the self mutilator. And if you listen closely, you can hear other stories much like the sort of story you might tell, if the mutilator were a friend, a parent or a relative.
If the question is more simply an intellectual question, let me know that, and maybe I can give you more information of that sort. If you want some more information of this sort, please let me know, and I'll try to supply whatever information that I can offer there as well. I'd like to be as helpful as I can.
Yours, Bob Kaven