Acne is one of the most common and distressing of skin diseases commonly present during adolescence and usually (but not always) resolves in early adult life. Seventy percent of the population develop acne, but only a relatively small proportion seek
medical attention. Several variants of acne are recognized, including infantile acne, which occurs on the face during the first few months and usually settles spontaneously, and occupational acne, resulting from exposure to oil, coal tar, chlorinated hydrocarbons, or insecticides. Acne may be precipitated or exacerbated by certain combined oral contraceptive pills or by androgenic hormones.
Acne vulgaris commonly affects the face, chest, and upper back, and usually presents during puberty. The clinical features include an increased rate of sebum secretion, comedones, papules, and pustules (Fig. 3). Severe acne may be complicated by atrophic or nodular keloid-type scars or by the formation of chronic nodules and cysts (Fig. 4).
Patients with acne tend to have a higher sebum excretion rate than others, and there is a degree of correlation between the sebum secretion rate and the severity of the acne (11,12). Circulating androgens stimulate the sebaceous glands with resulting hypertrophy and increased sebum secretion. Furthermore, there is abnormal keratin-
ization of the epithelium lining the hair follicle, which may lead to obstruction of the follicle with resulting comedone (blackhead) formation. Propionibacterium acnes, a gram-positive commensal bacterium, proliferates within the obstructed hair follicle, and may break down the lipid esters of sebum to liberate potentially irritating fatty acids (13). Eventual rupture of the wall of the obstructed follicle and the release of fatty acids into the surrounding dermis will result in an inflammatory response.
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