Yes, PETECHIAE is a Scrabble word!

Letter values in Scrabble US: P 3, E 1, T 1, E 1, C 3, H 4, I 1, A 1, E 1.

Is it a valid word?

PETECHIAE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a minute red or purple spot on the surface of the skin as the result of tiny hemorrhages of blood vessels in the skin (as in typhoid fever)