The Pathogenesis of Acne Part 2
Four Pathogenic Factors in Acne
o Excessive secretion of sebum is a necessary prerequisite for the onset of acne.
o Epithelial cells in the sebaceous follicles undergo abnormal desquamation. The combination of abnormally desquamated cells and excessive sebum form a microcomedo the precursor lesion of both no inflammatory comedones and inflammatory lesions.
o The anaerobic bacterium Propionibacterium acnes proliferates in the lipid-rich environment of the microcomedo.
o Acne produces proinflammatory mediators and chemotactic factors that can cause microcomedones to inflame and evolve into papules, pustules, and nodules.
Hormones in Acne
o Most acne patients probably have sebaceous glands that are hypersensitive to the effects of androgens.
o The most important hormones in the pathogenesis of acne are testosterone and dihydrotestosterone (DHT).
o Women with signs of virilization may have excess androgen production and need to undergo a hormonal work-up.
Topical Retinoids Render Follicles Inhospitable to P acnes
o Topical retinoids such as adapalene (DifferinÂ®), or tretinoin (Retin-AÂ®, Retin-A MicroTM, or AvitaÂ®) are the treatment of choice for normalizing follicular epithelial desquamation and making the environment less favorable for P acnes proliferation.
o The application of adapalene or tretinoin results in a "less plugged" follicle.
o To achieve optimal results, topical retinoids should be used for several months.
o Combination therapy with antibiotics, either topically or systemically, makes sense for most patients.
o For mild inflammatory acne: daily applications of a topical retinoid along with a combination of benzoyl peroxide with erythromycin.
o For mild to moderate inflammatory acne, either adapalene or tretinoin with benzoyl peroxide, or topical retinoids with a combination of benzoyl peroxide/erythromycin.
o Depending on severity, some patients may need to use both an oral and a topical version of a single antibiotic.
o Patients with large lesions can be treated with a local injection of a corticosteroid.
o Patients with nodular, cystic lesions may respond to oral antibiotic therapy alone. Some may require the systemic retinoid isotretinoin. In women, hormonal therapy with or without spironolactone is another option.
o For women with excessive ovarian androgen production, oral contraceptives containing estrogens or progestins are a good choice.
o Acne fulminans usually responds to oral corticosteroids.
o Acne surgery can be used if there are a large number of comedones, and the patient has applied topical retinoids for 1 to 2 months.