What Causes Reddish Purple Mark Between The Forehead And Nose Bridge?

my 6 yr old daughter hd a reddish purple mark appear on her forehead after a fever and vomiting and since then (July) it has grown from her hairline down the bridge of her nose. The dermatologist has ruled out Lichen Striatus and Morphea. What else could it be? No pain, not vascular, not raised. The discoloration is under the skin