Treatment for Large Birthmark on Legs?

An evaluation by your physician can determine whether this "birthmark" discoloration is vascular in origin (that is due to blood vessels beneath the skin) or hyperpigmentation (darkened discoloration of the skin). Either way there are various lasers that may be used to treat the area based on the underlying cause as well as your ethnicity. Seek out a physician with experience in laser treatments for various skin problems.