Curls and Birthmark

Here's some pics of the blond curly hair. It's only this curly right after he has a bath but we still enjoy it.
A couple weeks ago, when he was 5 weeks old, he had a really bad diaper and I had to end up bathing him. While I was bathing him I saw these brown spots on his belly a I thought it was poop. I kept scrubbing and scrubbing and it didn't come off. When I dried him off I realized it wasn't just on his belly. Well as the week went on the brown spots kept getting darker. So I called and got him into the doctor. His doctor was stumped as to what it was. He said it looked like birth mark material but it was so wide spread. Who knew a BIRTH mark could show up 5 to 6 weeks AFTER birth. But they said it can happen. So he sent us to a dermatologist. The dermatologist said it was definitely a malformation in the pigment of his skin. He had one of the nurses take a ton of pictures so he could show them to all his colleagues to see if any of them could diagnose/"give it a name". He also said not to be surprised if it continues to get darker. Well it has continued to darker so who knows just how dark it will get. If you look at the last picture closely you can see a definite line from his belly button down to his private. The doctor said something about us being A-symmetrical and the nerves in the body don't cross the center so that's why the discoloration stops at the middle of his body. So it starts at his belly button and goes around to his butt cheek and all down his thigh to just past his knee. The doctor said it definitely didn't look dangerous or something we needed to worry about but that he wanted to find out what to call it. So we are waiting to hear back from him after he talks to all his doctor buddies. We'll let ya know when we here something and update with more pics if we need too as or if it gets darker.