I have 5 parallel marks on my back. Don't remember how it happened, although my mom did tell me that when I was 10 I ran into her room in the middle of the night saying a demon scratched me. Don't know if that was the night or not, but the marks are still raised and are perfectly spaced apart.

May be growing/stretch marks of some kind, has just always been strange to me that they are horizontal and perfectly spaced.