The Importance of Inhibiting the Microcomedo
• Either topical or systemic retinoids can normalize keratinization within the follicle, and thus prevent the cohesion of follicular cells that leads to the formation of a microcomedo.
• Without intervention, the microcomedo may proceed either on a noninflammatory pathway to form mature comedones. Open comedones (blackheads) or closed comedones (whiteheads) - or on an inflammatory pathway to form papules, pustules, and nodules.

The Four Pathogenic Factors Involved in
• An increase in the levels of androgens before and during adolescence leads to the production of greater amounts of sebum.
• The bacterium Propionibacterium acnes, which is resident on the skin of even healthy individuals, thrives on sebum. Increased sebum production in patients results in a proliferation of this micro-organism.
• Something goes awry in the infundibulum of the follicle in patients that causes cells from the follicle wall to clump together. This abnormal keratinization results in the clogged pores, or microcomedones, that can later proceed to other lesions.
• The presence of P acnes triggers the release of chemotactic factors that cause inflammation, as manifested by papules, pustules, and nodules.
Retinoids Help Normalize Keratinization
• Although the mechanism by which topical and systemic retinoids help restore follicles to a healthy state is unknown, it has been well demonstrated that they normalize keratinization within the infundibular region of the follicle, so that shed follicular cells slough to the surface of the skin rather than clump together and obstruct the pores.
• After exposure to retinoids, follicular cells actually turn over more rapidly than they would in a pre-acne state.
• Retinoic acid has a high affinity for the gamma retinoid receptors, which are believed to be integral to the pathogenesis of acne.
• In addition to their ability to reverse abnormal keratinization within the follicle, the topical retinoids  - especially adapalene (Differin®), a naphthoic acid derivative - may have anti-inflammatory properties and thus may address two factors involved in the development of acne.

Addressing Patient Concerns
• In addition to effectiveness, patients are concerned about the level of irritation they may experience while on therapy.
• Some patients who used tretinoin in the past may be reluctant to try it again. For these patients, a gentler formulation, such as adapalene, might be the best first choice for a topical retinoid.
• Women who wear cosmetics might also prefer adapalene because its gel formulation is compatible with most makeups, allowing easy and smooth application with no pilling.

Safe at Any Age
• Topical retinoids can be used at any age.
• Even infants with clogged pores can benefit from a topical retinoid.
• Pregnant or nursing mothers should be dissuaded from using any drugs, except for topical erythromycin, although the evidence thus far suggests that topical retinoids are safe.
Enhanced Quality of Life
• Patients who have often report an increase in their quality of life once their skin clears.
• The difference in quality of life is most dramatic in patients with severe disease who use systemic retinoids, but patients who use topical retinoids also are happy about the improvement in their skin.
• Proper use of retinoid is a rewarding part of dermatologic practice.