This is an artist reproduction of what is seen histologically in various
acne lesions: The closed comedo (top center) can rupture and form
a pustule (mid-left), or a red papule (mid-right), or a large red
nodule (bottom center). It appears that the degree of inflammatory
response to the ruptured comedo is genetically modulated, i.e., bad
acne in parents or grandparents often leads to bad acne in their
progeny.