PROVIDENCE, R.I. (May 3, 2004) -- Researchers have successfully demonstrated a possible role for bacteria associated with microscopic mites -- known as Demodex folliculorum -- in the development of subtype 2 (papulopustular) rosacea, an increasingly common facial condition characterized by persistent redness with papules (bumps) and pustules (pimples), according to study results presented during the annual meeting of the Society for Investigative Dermatology here. It is estimated that rosacea affects more than 14 million Americans.

In the National Rosacea Society-funded study, Dr. Kevin Kavanagh and colleagues at the National University of Ireland-Maynooth found that the bacterium Bacillus oleronius stimulated an immune system response, inducing high levels of T-cell proliferation, in 79 percent of patients with subtype 2 rosacea, compared with only 29 percent of patients without the disorder. T-cell proliferation induces an inflammatory response, evident as papules and pustules.

"This indicates that the Bacillus bacteria found in the Demodex mite produce an antigen that could be responsible for the tissue inflammation associated with papulopustular rosacea," Dr. Kavanagh said.

The researchers located the bacteria in Demodex folliculorum, which are normal inhabitants of human skin. Because these microorganisms often occur in much greater numbers in patients with rosacea, researchers have long theorized that they may play a part in the development of the disorder.

"There are several possibilities that may explain how Demodex and bacteria interact to cause inflammation in rosacea," Dr. Kavanagh said. "For example, the Demodex mites may carry the pathogenic bacteria into areas of the face susceptible to the changes of rosacea, so that the increased mite density in rosacea patients may result in a higher density of bacteria that produce the papules and pustules. Alternatively, Demodex mites may be attracted to an area of facial skin rich in these bacteria and increase in numbers in this 'fertile territory.'"

Another possibility is that the mites in rosacea patients are infected with these bacteria, which in turn produce stimulatory antigens that trigger the disorder in susceptible patients, he said.

Dr. Kavanagh noted that the potential role for bacteria in causing papulopustular rosacea is supported by the fact that typical treatment for rosacea initially includes oral antibiotics that destroy B. oleronius. Interestingly, he said, antibiotics that are not harmful to these bacteria generally are not effective in the management of rosacea.

Moreover, the possibility that antigens may play a role in disease processes has been demonstrated in other disorders. For example, antigens produced by Streptococcus and Staphylococcus bacteria have been linked with such disorders as psoriasis, food poisoning and toxic shock syndrome.

Dr. Kavanagh and his colleagues are now developing antibodies against the antigen produced by B. oleronius to confirm its presence on the faces of patients with papulopustular rosacea and to define its relationship with Demodex mites.

Rosacea typically first appears after age 30 as a sustained flush, blush or redness on the cheeks, nose, forehead or chin that may come and go. Over time, the redness becomes ruddier and more persistent, and telangiectasia (visible blood vessels) may appear, a condition known as subtype 1 (erythematotelangiectatic) rosacea.

Bumps and pimples often develop along with persistent redness, a pattern of symptoms known as subtype 2 (papulopustular) rosacea, which is frequently seen with or following subtype 1. Some individuals, especially men, develop subtype 3 (phymatous) rosacea, which is characterized by thickening of the skin and often results in enlargement of the nose from excess tissue.

In many patients, the eyes are also affected, a condition known as subtype 4 (ocular) rosacea. In these cases, the eyes may appear watery or bloodshot, and irritation, burning, stinging, dryness, itching and light sensitivity are common symptoms. Styes may occur in ocular rosacea, and in severe cases loss of vision may result from corneal complications.

Patients often experience characteristics of more than one subtype, and in most cases some rather than all potential signs and symptoms appear in any given individual.

For more information and educational materials on rosacea, write the National Rosacea Society, 111 Lions Dr., Ste. 216, Barrington, Illinois 60010, or call its toll-free number at 1-888-NO-BLUSH. Information and materials are also available on the society's Web site at www.rosacea.org or via e-mail at info@rosacea.org.