abnormal formation or arrest of differentiation of the sebum-producing epithelial cells of the sebaceous glands that release their content by rupture of the cell membrane and cellular degradation; these cells are most commonly found in the skin in association with hair follicles (forming the pilosebaceous unit), where they arise from hair follicle keratinocytes, but there are also sebaceous glands not associated with a hair follicle; the latter have special functions as secretion of pheromones or corneal protection; sebocyte differentiation is defined by increasing accumulation of lipid droplets, the major component of sebum