A genetic variation that results in an inherited urticaria-inducing reaction to vibration has been found by researchers from the U.S. National Institutes of Health (NIH), providing new insight into a rare condition, according to a paper published online in The New England Journal of Medicine (Feb. 3, 2016).
The authors found that patients with a previously unidentified missense substitution in the adhesion G protein-coupled receptor E2 (ADGRE2) gene (also known as EMR2) experience an exaggerated version of a normal cellular response to vibration. According to a NIH press release, individuals with the condition can experience temporary skin rashes caused by running, hand clapping, towel drying or even from a rough motor vehicle ride.
The ADGRE2 protein has two sub-units which are generally found on the outside and inside of the walls of immune cells, including mast cells. The study’s authors speculate that in patients who experience vibration-induced urticaria, the two subunits are more weakly connected. Vibration then causes these two subunits to become separated, leading to the internal subunit to signal the cell to start degranulation.
As part of the process of degranulation, mast cells release histamine and other inflammatory chemicals into the bloodstream and surrounding tissue in response to certain stimuli, according to the release, and when researchers measured blood levels of histamine during an episode of vibration-induced urticaria, they found the patient’s histamine levels rose rapidly after the vibration and then subsided after about an hour. As well, an increase in another mast cell degranulation marker, tryptase, was also seen in the skin around the hives.
“Investigating rare disorders such as vibratory urticaria can yield important insights into how the immune system functions and how it reacts to certain triggers to produce allergy symptoms, which can range from mild to debilitating,” Dr. Anthony S. Fauci, director of the U.S. National Institutes of Allergy and Infectious Diseases (NIAID), said in the realease.. “The findings from this study uncover intriguing new facets of mast cell biology, adding to our knowledge of how allergic responses occur.”
According to the release, individuals who experience vibratory urticaria sometimes also have other symptoms, including flushing, headaches, fatigue, blurry vision or a metallic taste in the mouth. These symptoms usually last an hour or less but can show up several times a day.