Yes, MONGOLISMS is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, N 1, G 2, O 1, L 1, I 1, S 1, M 3, S 1.

Is it a valid word?

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

a congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation

Also: down's syndrome, down syndrome, trisomy 21.

Not playable in Scrabble US: MONGOLIANISM.