Rosacea, a disease that produces pustules, redness and small surface blood vessels in patients over the age of 30 can look exactly like pustular acne.
Hidradenitis suppurativa is a disease with a hereditary predisposition. Painful cysts can occur under the arms, under the breasts, in the groin and around the buttocks. Open comedones (blackheads) with 2 or 3 openings are a cardinal feature of this disease.
Folliculitis caused by bacteria can resemble pustular acne. A special form of folliculitis called gram-negative folliculitis occurs in the chin area following long-term use of oral antibiotics.