My 4 years old son has brown patches and pigmentation over the trunk.It was last summer when i noticed few pigmentation on his chest which has now increased to many brown patches. He itches badly. I just thought may be due to heat or sun exposure but he itches even in cool or when not in the sun. He also gets hives frequently on those areas. I'm planning to get an appointment with the dermatologist, but before that i wanted to know if someone here has the same condition or can suggest me what could be the condition my son is suffering from.

Thank you very much.