What is polymyositis and dermatomyositis

Polymyositis and dermatomyositis is an autoimmune connective tissue diseases. The rest of the world have the disease incidence, But the incidence rate is not high, the estimated incidence rate of 0.05 - 0.84/10 million people, with the understanding and diagnosis of the disease raises the level of the incidence rate tended to rise. China has yet to conduct epidemiological studies, the incidence rate is not clear. The disease can be found in any age, but there are two peak periods, the first peak in the 10 to 15-year-old, the second peak in 45-60 years old, associated with cancer patients aged 60 or so. Female patients about twice the men. Also affected different ethnic polymyositis and dermatomyositis incidence. According to reports, the Japanese have a low incidence rate, and black people the highest incidence rates. The polymyositis and dermatomyositis exact etiology is not clear, may be infected, genetic, immunology, cancer, and other factors. Research has found that many infections, such as HIV infection, bacterial infections, fungi and protozoa infection and the disease related to virus infection in the pathogenesis of this disease may play an important role. After the infection, promote and induced autoimmune reaction caused chronic protracted process. The human leukocyte antigen (HLA) study found that HLA-DR3 positive individuals in juvenile dermatomyositis and polymyositis an increase in the frequency. Therefore, polymyositis and dermatomyositis and genetic factors, but the incidence of familial aggregation rare. The majority of patients the disease autoantibodies appeared that the disease pathogenesis and immune abnormalities. As many polymyositis and dermatomyositis patients with cancer, and some patients after resection of tumor, the disease also has been eased, it was that tumors secrete a toxin may directly cause the disease lesions. In addition, immunization, chloroquine, cocaine, colchicine, penicillamine, lipid-lowering drugs, and other drugs, alcohol, intoxication, trauma, surgery can also cause or induce the occurrence of this disease.