Page 51 - LECTURE NOTES

forms. Acne vulgaris affects the areas of skin with the densest population of

sebaceous follicles; these areas include the face, the upper part of the chest, and the
back.

Four key factors are responsible for the development of an acne lesion:

1. Follicular epidermal hyperproliferation and hyperkeratinization, the increased

level of adrenal derived androgen, dehydroepiandrosterone sulfate induces
hyperproliferation.

2. Excess sebum, - Excess sebum is also a key factor in the development of acne

vulgaris. The amount of sebum produced and the degree and the severity of the acne

are strongly correlated. Sebum excretion is under hormonal control. Androgens
stimulate sebocyte differentiation and sebum production, whereas estrogens have an

inhibitory effect. Most men and women with acne have normal circulating levels of
androgen hormones. An end-organ hyperresponsiveness to androgens has been

hypothesized.

3. Propionibacterium acnes, - P acnes is a microaerophilic organism present in

many acne lesions. P acnes stimulate inflammation by producing proinflammatory
mediators that diffuse through the follicle wall.

4. Inflammation - Inflammation may be a primary phenomenon or a secondary
phenomenon and plays a role in the development of acne comedones, papules,

pustules, and nodules in a sebaceous distribution characterize acne vulgaris. The face

may be the only involved skin surface, but the chest, the back, and the upper arms are
often involved

5. Genetic predisposition – but mode of inheritance is unknown

6. Mechanical factors – excessive rubbing of the skin and use of oily cosmetics may
induce acne lesion.

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