Dark purple bruises have appeared on my grandma's arms - they don't cause pain, but have spread over the span of a few days?

Purpura?: Is described as: hemorrhagic states characterized by patches of purplish discoloration resulting from extravasation of blood into the skin and mucous membranes. Sometimes the aging process itself with thinner skin etc. are risk factors alone to get this, however, it is best to have grand mom see her Doctor to get them clinically evaluated and even some labs may need to be done. Best wishes.