Yes, DYSTROPHIES is a Scrabble word!

Letter values in Scrabble US: D 2, Y 4, S 1, T 1, R 1, O 1, P 3, H 4, I 1, E 1, S 1.

Is it a valid word?

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

any of several hereditary diseases of the muscular system characterized by weakness and wasting of skeletal muscles
any degenerative disorder resulting from inadequate or faulty nutrition

Also: muscular dystrophy.