Different types of ANCA-associated vasculitis occur in different ethnic groups, a study reports.
The research, “Global ethnic and geographic differences in the clinical presentations of anti-neutrophil cytoplasm antibodyassociated vasculitis,” was published in the journal Rheumatology.
Anti-neutrophil cytoplasm antibodies-associated vasculitis, or AAV, refers to three rare diseases: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA).
Hallmarks of the disease are cell inflammation and the destruction of blood vessel walls.
AAV is an autoimmune disease, or one that involves the immune system attacking healthy tissue. The way the immune system does this is by producing autoantibodies, or antibodies that go after some of the body’s own proteins.
In the case of AAV, the autoantibodies target two proteins found in neutrophils, a type of white blood cell. The proteins are known as proteinase 3 (PR3) and myeloperoxidase (MPO). Patients with AAV usually have autoantibodies against one of the proteins, but not both. The autoantibody that targets PR3 is PR3-ANCA, and the one that targets MPO is MPO-ANCA.
Studies have suggested that certain types of AAV are more common in some parts of the world than others, but there has been little information on whether different types of AAV show up in different ethnic groups.
A group of researchers decided to see if they could find an association.
The team used information from the Diagnostic and Classification of Vasculitis (DCVAS) study. It covered 1,217 AAV patients at 133 medical centers in 33 countries between 2014 and 2016.
Researchers discovered that PR3-AAV was most common in northern Europeans. Sixty-one percent had this form of the disease. In contrast, 81 percent of Japanese and 45 percent of Chinese had MPO-AAV. The prevalence of PR3-AAV and MPO-AAV was similar among Caucasian Americans and southern Europeans.
Another finding was that people of Middle Eastern and Turkish origin were more likely to have MPO-AAV than northern Europeans.
In addition, ANCA-negative AAV — a form of the disease in which patients lack ANCAs — was most frequent among Chinese and least frequent among northern Europeans. The figures were 33 percent of Chinese and 14 percent of northern Europeans.
When the researchers examined the symptoms of the disease by ethnic group, they found that manifestations were less common in Japanese patients than in northern Europeans. Ear, nose and throat manifestations were less common among Japanese and Chinese than northern Europeans. Another discovery was that, compared with northern Europeans, kidney manifestations of AAV were most common among Middle Easterners, Turks, Indians, Pakistanis, and Bangladeshis, and least common among Caucasian Americans.
A key limitation of the study was that few people in some ethnic groups were among the more than one thousand patients examined.
Nevertheless, the researchers concluded that the study “confirms the previously observed differential occurrence of MPO-AAV and PR3- AAV” in different parts of the world.