Question about my rare birthmark.

Hey everyone. I have a few questions reguarding my birthmark.
There should be a photo attached, but incase you can't see it - http://img121.imageshack.us/img121/1241/spa0341o.jpg. It covers my left arm, my left chest and most of my back. I've had it from birth (duh). I can't remember what it was called even if it did have a name, no one seems to know anything about it from where I am anyway, so I thought I'd ask here.
Discription - Either in long bands or random dispersal; flaky mixed with rough discoloured skin.
Depending on how it feels in the morning, it can be generally very sore, and used to itch like hell when I was younger, nowerdays it can act up every often, and even if I accidently catch it on something, it'll generally bleed quite easily.
I was wondering if anyone had any information on it. Thanks.