People who suffer itching with no clear cause may have previously unrecognized immune system defects. “As doctors, we throw things like antihistamines, ointments and lotions at patients who suffer chronic itching, but if there is something profoundly abnormal about the immune system — as it appears there is — then we can’t solve the itching until we address those underlying causes,” says Washington University dermatologist and researcher Brian Kim, MD.
"The immune system needs to be in balance, and we hope to find ways to restore that balance in patients with this very debilitating condition.”
Kim and other researchers from the Center for the Study of Itch at Washington University School of Medicine conducted a small study of people that identified immune-system irregularities that may prompt the urge to scratch. In the study, researchers took blood samples and skin biopsies from participants to look for immune problems. They found “an incredible amount of dysfunction,” Kim says, adding that he has seen similar defects in numerous additional patients not included in the current study.
In this study, the four people researchers zeroed in on were ages 75 to 90. In blood samples, three of those four had high levels of the protein IgE — an immunoglobulin that is a marker of inflammation.
Immunoglobulins are antibodies deployed by the immune system to fight infections. Elevated levels of IgE are often seen in people with allergies. The research team also noted very low levels of an immunoglobulin known as IgG; abnormally low counts of a type of immune cell called a CD8 T-cell; and an elevated number of immune cells called eosinophils, which are markers of allergic inflammation.
“Curiously, none of these patients had any history of allergic disorders,” Kim says. “We often see similarly high counts of eosinophils in patients with eczema, but the patients we studied didn’t have eczema. They didn’t even have a rash. Only itching.”
Kim notes that dermatologists frequently take skin biopsies when a patient has a rash, but with chronic itching of unknown origin, also known as chronic idiopathic pruritis, there is nothing evident to biopsy. The study’s first author, Amy Xu, a medical student in Kim’s lab, says most people with this type of unexplained itching tend to be older and develop itching problems later in life. “It may be caused by some sort of wear and tear on the immune system,” Xu says.
Because of the small number of people in the study, it’s too soon to draw firm conclusions, but the itching may be an indication that something else in the body is going wrong, Kim says. “We have begun working on a mouse model in which the animals have similar defects,” he adds. “We want to learn whether these changes in the immune system create only itching or whether they could be signs that some other problem is present.”