Rosacea is a common, persistent dermatologic disorder of the central face affecting an estimated 10% of the world’s population.1 Despite its high prevalence, the pathogenesis of rosacea remains unclear and management with the limited treatments available is insufficient in most cases. In the United States, where approximately 16 million people are affected by rosacea, treatment focuses largely on the avoidance of triggers, such as sun exposure, extreme heat or cold, heavy exercise, spicy foods, alcohol consumption, and smoking.2,3 Recently, however, small strides have been made in the understanding of its pathogenesis, and in the development of newly approved topical therapies that may help improve the outcomes of rosacea.1,4
The broad range of rosacea presentations led to it being subdivided in 2002 into 4 major subtypes: erythematotelangiectatic (ETR), papulopustular (PPR), phymatous (PHY), and ocular rosacea (OR), based on distinct patterns of symptoms.5 ETR was defined primarily by the presence of telangiectasia, erythema, and flushing. While PPR also includes erythema and flushing, it is accompanied by papules and pustules. PHY involves thickening of the skin and hypertrophy of the nose, and the symptoms of OR occur mostly around the eyes, including tearing, stinging, itching, and dryness of the lids.2,4,5 Rosacea is not limited to these symptoms, which may also overlap between subtypes and progress, complicating diagnosis according to these categories alone.
A Changing Diagnostic Paradigm
No single definition of rosacea has been accepted, although the presence of any of the most common signs of flushing, non-transient erythema, papules and pustules, and telangiectasia, are indicative of a rosacea diagnosis.5 Recent investigations have helped identify phenotypic characteristics that may have more relevance in the effective treatment of rosacea on an individual level. A newer approach based on the constellation of both major and secondary features requires only the persistence of central facial erythema and phymatous changes for a diagnosis of rosacea.2 Other symptoms, such as flushing, telangiectasis, and the presence of papules or pustules are suggestive, but may only be used in combination for a diagnosis.
At the same time, the known genetic features of rosacea — that it tends to affect light-skinned people and is particularly prevalent in individuals of Celtic heritage — may reflect underestimations of the disorder in many areas of the world.2
Potential Pathophysiologic Mechanisms
Some studies have linked colonization with demodex mites to rosacea, although treatments that eradicate the mites failed to significantly improve the clinical symptoms of rosacea.2 A weak association with Helicobacter pylori has also been found, but again, successful treatment of the former did not substantially affect rosacea.2