Despite the fact that inflamed lesions are usually of greatest concern to the patient, less is known about their development than is known about sebum production, comedogenesis and the role of bacteria in the aetiology of acne.

 

  The  clinical features of inflamed lesions, which  can be divided into  the superficial  and deep types,  are described  in  detail elsewhere. The superficial lesions include active papules, less  active papules,  active  pustules, less  active pustules and macules - an important end phase of most inflamed lesions. Deep lesions are either nodules, deep pustules or, the least common, cysts.