Acne vulgaris is a common chronic skin disease involving blockage and/or inflammation of pilosebaceous units (hair follicles and their accompanying sebaceous gland). Acne can present as noninflammatory lesions, inflammatory lesions, or a mixture of both, affecting mostly the face but also the back and chest.
Acne vulgaris has a multifactorial pathogenesis, of which the key factor is genetics. Acne develops as a result of an interplay of the following four factors: (1) follicular epidermal hyperproliferation with subsequent plugging of the follicle, (2) excess sebum production, (3) the presence and activity of the commensal bacteria Propionibacterium acnes, and (4) inflammation.
Acne occurs through the interplay of 4 major factors:
Excess sebum production
Follicular plugging with sebum and keratinocytes
Colonization of follicles by Propionibacterium acnes (a normal human anaerobe)
Release of multiple inflammatory mediators
The most common trigger is
During puberty, surges in androgen stimulate sebum production and hyperproliferation of keratinocytes.
Other triggers include
Hormonal changes that occur with pregnancy or the menstrual cycle
Occlusive cosmetics, cleansers, lotions, and clothing
High humidity and sweating
Associations between acne exacerbation and diet, inadequate face washing, masturbation, and sex are unfounded. Some studies suggest a possible association with milk products and high-glycemic diets. Acne may abate in summer months because of sunlight’s anti-inflammatory effects. Proposed associations between acne and hyperinsulinism require further investigation. Some drugs and chemicals (eg, corticosteroids, lithium, phenytoin, isoniazid) worsen acne or cause acneiform eruptions.
Acne results in a variety of lesions. The most common acne locations include the face, neck, chest, and back, where the most sebaceous glands are located. Along the jaw line is a common location in adults. "Blackheads" (open comedones) and "whiteheads" (closed comedones) are follicular plugs that are either sitting below the skin surface (whitehead) or oxidized from being exposed to the air (blackhead). Papules are small pink to reddish-brown bumps, pustules are pus-filled lesions, and nodules or cysts are deeper pus-filled lesions.
Mild acne consists of a few papules/pustules and/or comedones. Moderate acne has an increased number of lesions. Severe acne has numerous comedones, papules, pustules, and may have painful nodules.
Acne can result in permanent scars, which can appear to be depressions in the skin or hyperpigmentation, which is dark red or brown flat marks where the acne lesions were.
Comedones: Topical tretinoin
Mild inflammatory acne: Topical retinoid alone or with a topical antibiotic, benzoyl peroxide, or both
Moderate acne: Oral antibiotic plus topical therapy as for mild acne
Severe acne: Oral isotretinoin
Cystic acne: Intralesional triamcinolone