Acne is a common, usually self-limiting disease involving inflammation of the sebaceous follicles of the face and upper trunk.
WHAT ARE THE CAUSES OF ACNE VULGARIS?
Acne usually begins in the prepubertal period and progresses as androgen production and sebaceous gland activity increase with gonad development.
Acne progresses through four stages: (1) increased sebum production by sebaceous glands, (2) Propionibacterium acnes follicular colonisation (and bacterial lipolysis of sebum triglycerides to free fatty acids), (3) release of inflammatory mediators, and (4) increased follicular keratinisation.
Circulating androgens cause sebaceous glands to increase their size and activity. There is increased keratinisation of epidermal cells and development of an obstructed sebaceous follicle, called a microcomedone. Cells adhere to each other, forming a dense keratinous plug. Sebum, produced in increasing amounts, becomes trapped behind the keratin plug and solidifies, contributing to open or closed comedone formation.
The pooling of sebum in the follicle facilitates the proliferation of the anaerobic bacterium Propionibacterium acnes, which generates a T-cell response resulting in inflammation. P. acnes produces a lipase that hydrolyses sebum triglycerides into free fatty acids that may increase keratinisation and lead to the microcomedone formation.
The closed comedones (Whitehead) is the first visible lesion of acne. It is almost completely obstructed to drainage and tends to rupture.
An open comedone (blackhead) is formed as the plug extends to the upper canal and dilates its opening. Acne characterised by open and closed comedones is termed noninflammatory acne.
Pus formation occurs due to the recruitment of neutrophils into the follicle during the inflammatory process and release of P. acnes–generated chemokines. P. acnes also produces enzymes that increase the permeability of the follicular wall, causing it to rupture, thereby releasing keratin, lipids, and irritating free fatty acids into the dermis. Inflammatory lesions that may form and lead to scarring include pustules, nodules, and cysts.
WHAT ARE THE SIGNS AND SYMPTOMS OF ACNE VULGARIS?
Lesions usually occur on the face, back, upper chest, and shoulders. Severity varies from a mild comedonal form to severe inflammatory acne. The disease is categorised as mild, moderate, or severe, depending on the type and severity of lesions.
Lesions may take months to heal completely, and fibrosis associated with healing may lead to permanent scarring.
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