Yes, PELLAGRAS is a Scrabble word!

Letter values in Scrabble US: P 3, E 1, L 1, L 1, A 1, G 2, R 1, A 1, S 1.

Is it a valid word?

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

a disease caused by deficiency of niacin or tryptophan (or by a defect in the metabolic conversion of tryptophan to niacin); characterized by gastrointestinal disturbances and erythema and nervous or mental disorders; may be caused by malnutrition or alcoholism or other nutritional impairments

Also: alpine scurvy, mal de la rosa, mal rosso, saint ignatius' itch.

Not playable in Scrabble US: MAIDISM, MAYIDISM.