pyoderma gangrenosum

noun

pyoderma gan·​gre·​no·​sum -ˌgaŋ-gri-ˈnō-səm 

: a chronic noninfectious condition that is marked by the formation of purplish nodules and pustules which tend to coalesce and form ulcers and that is associated with various underlying systemic or malignant diseases (as leukemia, ulcerative colitis, rheumatoid arthritis, or metastatic adenocarcinoma of the intestine)