Rosacea is a disorder of poorly understood origin (Steinhoff, 2013). Rosacea is a chronic skin disorder affecting primarily the central face (cheek, nose, chin and forehead). Over 13 million Americans have this condition and is the 5th most common reason to visit a dermatologist. A standard classification system for rosacea was published in the Journal of the American Academy of Dermatology in 2002. Developed by the National Rosacea Society Expert Committee on the Classification and Staging of Rosacea and reviewed by rosacea experts worldwide, it describes primary and secondary features of rosacea and recognizes 6 patterns of signs and symptoms, designated as subtypes. These include: flushing, vascular congestion (erythema or redness), increased vascularity, papulopustular skin lesions (pustules or enlargement of the oil glands) and thickening of the skin. Ocular involvement includes damage to the meibomian glands with subsequent dry eyes, conjunctiva and sclera inflammation with subsequent risk for corneal damage and loss of visual acuity. A seventh pattern being proposed is flushing and erythema with pain as being the main problem – this painful rosacea may consist of the following symptoms: burning, stinging and irritation.
The various clinical forms of rosacea exhibit very different clinical features and trigger factors which suggest that rosacea is a disorder of multiple causes. The fact that a person may have one or more forms with flushing, chronic inflammation and fibrosis further suggests a complex pathophysiology involving different regulatory systems. Despite active research into the interplay of the various dysregulated systems (immune, vascular, and nervous), the cause for rosacea remains a mystery. Altered regulation in the internal immune and neurovascular systems is very important. Genetics play a role, but, as in most diseases, one's genetic makeup influences the likelihood of developing rosacea after acquiring a triggering event.
What is the role of infections in the skin? A recent review addresses this question (Hughes, 2013). Studies support an inflammatory reaction against the presence of Demodex folliculorum, a naturally occurring mite. A few studies suggest roles for Staphylococcus epidermidis, Chlamydophila pneumoniae, and Bacillus oleronius; however, none of these studies provides a good understanding of the mechanism by which these bacteria trigger the development of rosacea.
The role of small intestinal bacterial overgrowth (SIBO) in the pathophysiology of rosacea is becoming a key factor, though its importance is not well-known amongst most physicians.