Researchers have solved a medical mystery that has eluded them for hundreds of years, demonstrating that an abundance of abnormal skin proteins causes the blotchy skin condition called rosacea.
In a study published Sunday in the journal Nature Medicine's online edition, scientists showed that people with rosacea had too much of an incorrectly processed protein called cathelicidin.
The results could aid researchers in designing an effective treatment for the disease affecting 14 million in the U.S.
"We haven't had this kind of important finding in the study of rosacea for a long time," said Dr. Jenny Kim, a dermatologist with UCLA's David Geffen School of Medicine, who was not involved in the study.
Rosacea is a skin disease that causes redness, visible blood vessels, bumps and pimples on the face. It tends to strike more women, usually between the ages of 30 and 60, but men often have more severe symptoms. "It's an appearance-related disease, so many people suffer from low self-esteem, and that can affect their everyday life," Kim said.
Options for treatment include light therapy to decrease redness, avoiding known triggers such as spicy foods and heat, and prescribing antibiotics that don't work for every patient.
"Treatment could now be much more rationally designed," said Dr. Richard Gallo, chairman of dermatology at UC San Diego and senior author of the study.
About a dozen years ago, researchers in Gallo's lab discovered cathelicidin proteins, which help defend against skin infections. Gallo and his colleagues went on to find an association between the protein and skin conditions such as eczema.
The team later found that cathelicidin could cause the redness that is the hallmark of rosacea, so they sought a link.
The researchers took skin biopsies from 11 people with rosacea and 10 without. What they found was "a double hit of things going abnormally," Gallo said.
All of the rosacea patients had too much cathelicidin, most of which was abnormal. There was also an abundance of a molecule that processes cathelicidin from an inactive to an active form. The way cathelicidin is processed is crucial to determining whether the protein will act as a defense against infection or promote inflammation, according to the study. Experiments on mice confirmed their theory.
One common treatment for rosacea is the antibiotic tetracycline. The study suggests that the drug is successful for patients because it inhibits cathelicidin processing, not for its bacterial-killing properties. Future treatments might also target the excessive production of cathelicidin's precursor, Gallo said.