• John Evans

Identified: Driver of itch in prurigo nodularis


Photo by Masryyy via Wikimedia Commons

Researchers have discovered a new mediator of itch in prurigo nodularis (PN), which they say could lead to new therapeutic options for the condition.


In a press release from Johns Hopkins University in Baltimore, the researchers note that there has been little research on PN and there are currently no U.S. FDA-approved treatments for the condition.


“There is an urgent need to better understand the development of this condition, which greatly impacts the lives of patients, causing unbearable itch, sleep disturbance and psychosocial distress,” senior author Dr. Shawn Kwatra, assistant professor of dermatology at the Johns Hopkins University School of Medicine, said in the release.


To better understand the causes of PN, investigators examined the relationship between skin cell messenger RNA and molecules circulating in the blood that mediate systemic inflammation.


The investigators collected and studied peripheral blood mononuclear cells (PBMCs) and skin biopsies from patients with PN and healthy subjects matched by age, race and sex. The majority of the participants were African American.


Studying the samples revealed that in the subjects with PN, elevated levels of interleukin-22 (IL-22) secretion by Th22 lymphocytes caused increased downstream pro-inflammatory signalling throughout the skin.


Further analysis found that these Th22 cells were part of a dysregulated immune pathway and correlated most strongly with patient-reported itch intensity.


“This study provides direct evidence that PN is a systemic inflammatory disorder, with circulating blood inflammation serving as a link between skin disease and other comorbidities, such as insulin resistance and high blood pressure,” Dr. Kwatra said. “Identifying the links between chronic itch conditions and other underlying health issues shows us that it is important for patients with PN to get treated early so the systemic inflammation does not contribute to the development of more serious health issues.”


The findings were published online ahead of print in The Journal of Investigative Dermatology (March 23, 2021).