Rosacea is seen more commonly among white Caucasians than in other ethnicities and is slightly more prevalent among females than males. A complication of rosacea called rhinophyma or nose deformity, however, is more common among males. The condition typically affects people aged between 30 and 60 years.
The causes of rosacea are unclear but are thought to involve the following:
- Genetic predisposition
- Altered blood vessel or vascular response to stimuli
- Altered immune response
Studies have shown that among patients with rosacea who develop reddish discoloration of the face with no presence of inflamed reddish bumps or pustules, there is overactivation of genes that regulate the inflammatory process as well as blood vessel dilation and constriction in response to inflammation.
Research also supports an increased inflammatory response following an enhanced innate immune response to various "triggers" including exposure to ultraviolet rays, certain foods and medications.
Although many studies favour a genetic element to the pathology of rosacea, no predisposing gene has yet been confirmed in humans.
One team of researchers, Schwab et al, (5) investigated whether the pathophysiology of rosacea involves neurogenic inflammation and therefore arises from the release of neuromediators from sensory nerves. Among different subtypes of rosacea, the team performed real-time PCR and gene array analysis as well as immunohistochemistry and immunflourescence studies to assess molecular and morphological characteristics. The findings were then compared with those for lupus erythematosus and for healthy skin.
The results showed that for all subtypes of rosacea, there was close anatomic association of sensory nerves, blood vessels and immune cells as well as evidence of neuroimmune and neurovascular interaction. Significant dilation of blood and lymphatic vessels was observed, along with increases in levels of mast cells (MCs) and fibroblasts (FBs). Interestingly, the increased MC and FB levels occurred in rosacea subtypes where fibrosis was not yet clinically apparent, suggesting inflammation is activated early on in disease course.
The RT-PCr data showed upregulation of receptors (eg, serotonin receptor HTR3A) that are targeted by mediators released from mast cells or sensory neurons. The researchers say the results suggest significant neurovascular and neuroimmune communication in the pathology of rosacea and that drugs which act on these processes may be beneficial in treatment.
Analysis of LE showed that blood and lymphatic vessel dilation were also increased but nerves, MC and FBs were not.
Research is ongoing in understanding the pathology and possible genetic connection to the immune responses associated with the development of rosacea.