Dermatologist Brian Kim has seen many patients who can't seem to stop itching. Often, it's difficult to determine what's causes the irritation, which can make deciding a course of treatment challenging.
"Most of the drugs I use only work a small minority of the time, so we have to be patient," said Kim, co-director of Washington University's Center for the Study of Itch. "But as you can imagine, as a patient, when you fail with three different medications, it can be incredibly frustrating."
Research done by Kim's predecessors suggested a link between chronic itch, a type of itch that lasts for more than several months, and irregularities in the immune system. Because little is known about what causes chronic itch, he decided to explore the connection between the two and found that the answer may be in a patient's immune system.
In a small study published recently in the Journal of the American Academy of Dermatology, Kim and his colleagues analyzed skin and blood samples from four elderly patients whose persistent itch was caused by an unknown source. Tests revealed that their immune systems were behaving unusually.
"I expected there to be defects, but I was most surprised by the extent of the defects," said Kim, an assistant professor of dermatology at Wash U.
For example, blood tests showed that the patients had very low levels of T-cells, the white blood cells that attack foreign invaders in the body.
One of the study's authors, Amy Xu, a medical student at Washington University, suggested that it's possible such abnormalities result from wear and tear on the immune system over time, since the patients were at least 75 years old.
Kim acknowledged that it's rare to see a chronic itch patient who is under 50 years old. However, not all elderly people have chronic itch. But he noted that some people's immune systems age faster than they do.
"So although they might be 70, their bone marrow might actually be 100 years old in terms of biologic age," Kim said.
Since the recent study analyzed only a small batch of patients, Kim's laboratory is now focused on understanding the connection between chronic itch and problematic immune systems, and whether older people are more likely to have chronic itch.