Continuing medical education
Rosacea: I. Etiology, pathogenesis, and subtype classification

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Abstract

Rosacea is one of the most common conditions dermatologists treat. Rosacea is most often characterized by transient or persistent central facial erythema, visible blood vessels, and often papules and pustules. Based on patterns of physical findings, rosacea can be classified into 4 broad subtypes: erythematotelangiectatic, papulopustular, phymatous, and ocular. The cause of rosacea remains somewhat of a mystery. Several hypotheses have been documented in the literature and include potential roles for vascular abnormalities, dermal matrix degeneration, environmental factors, and microorganisms such as Demodex folliculorum and Helicobacter pylori. This article reviews the current literature on rosacea with emphasis placed on the new classification system and the main pathogenic theories.

Learning objective

At the conclusion of this learning activity, participants should be acquainted with rosacea's defining characteristics, the new subtype classification system, and the main theories on pathogenesis.

Section snippets

Definition and subtypes

The April 2002 issue of this Journal contained an important article in which members of an expert committee assembled by the National Rosacea Society reported their conclusions of a meeting designed to standardize diagnostic criteria for rosacea.1 The defining characteristics are a loosely associated series of signs and symptoms. The presence of flushing, persistent erythema, telangiectasia, papules, and pustules in a central facial distribution is certainly enough to allow even dermatologic

Disease definition

The expert committee stated that the diagnosis of rosacea requires the presence of one or more of the following primary features concentrated on the convex areas of the face: flushing (transient erythema), nontransient erythema, papules and pustules, and telangiectasia.1 While we agree with the basic diagnostic criteria presented, we believe that additional refinements are needed. For instance, is a history of flushing in a central facial distribution enough to define rosacea? How long is the

Rosacea subtypes

It is of paramount importance to indicate the subtype of rosacea that is diagnosed, as there is a wide spectrum of patients for whom the umbrella term rosacea is commonly rendered. The classic patient at the midpoint of the spectrum—Wilkin's typological center—is easily recognized.5 It is likely that this epicenter was what originally separated rosacea most easily from other diseases. However, manifestations of rosacea are protean, involve multiple associated signs and symptoms, and are often

Glandular rosacea

One phenotype displayed in certain rosacea patients is quite different from the other 4 classic subtypes recognized above. We propose the term glandular rosacea (GR) to describe this phenotype, which is commonly seen and illustrated in textbooks (Fig 5, Fig 6) but has not previously been clearly separated into a distinct nosologic subtype. GR is most common in men who have thick, sebaceous skin. Edematous papules and independent pustules are often of large size, and nodulocystic lesions may be

Pathophysiology

The cause of rosacea remains unknown. Several factors have been implicated in its pathogenesis, some based on the evidence of scientific investigation, others on anecdotal observation. Proposed etiologic mechanisms can be grouped into the following categories: vasculature, climatic exposures, matrix degeneration, chemicals and ingested agents, pilosebaceous unit abnormalities, and microbial organisms. However, a central paradox remains; how does one explain the varied clinical expressions of

Future studies

Many aspects of rosacea require further investigation. It is our hope that this manuscript will stimulate some of these efforts. One area to approach in regard to pathophysiology is the possible follicular nature of the papules and pustules. Researchers should also investigate the role of P acnes in the formation of these inflammatory lesions. Concerning investigation into Demodex and H pylori, we suggest that future efforts be directed elsewhere. Despite exhaustive efforts in numerous studies,

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    Initial support for the clinical-educator fellowship program from which this study resulted was provided by a generous grant from Ronald Krancer to the Dermatology Section of the Pennsylvania Hospital, Philadelphia, in honor of his dermatologist, Paul R. Gross, MD.

    Conflict of interest: None identified.

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