Yes, CIRRHOSIS is a Scrabble word!

Letter values in Scrabble US: C 3, I 1, R 1, R 1, H 4, O 1, S 1, I 1, S 1.

Is it a valid word?

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

a chronic disease interfering with the normal functioning of the liver; the major cause is chronic alcoholism

Also: cirrhosis of the liver.