Dermatomyositis by what causes: 1, drug factors. Dermatomyositis induced drugs include ethanol, D-penicillamine, cimetidine, hydroxyurea, non-steroidal anti-inflammatory drugs, antibacterial drugs, lipid-lowering drugs (simvastatin), terbinafine, Root and vaccines. That the drug to promote human endothelial cell apoptosis, the body cell antigen translocation to produce new antigenicity, leading to anti-endothelial cell antibody formation, and promote the occurrence of dermatomyositis. These drugs can induce the typical clinical manifestations of dermatomyositis patients, such as the occurrence of dermatomyositis-like lesions, stimulate polymyositis, muscle weakness or muscle damage, serum creatase. 2, genetic factors. Genetic studies Although the disease is very small family aggregation phenomenon, but still believe that the incidence of dermatomyositis in a genetic tendency exists. At present, the relationship between phenotype of human leukocyte antigen and dermatomyositis is a hotspot in the study of etiology and genome level of dermatomyositis. 3, immune factors. Dermatomyositis is the main body of humoral immune injury, while the multiple myositis is the main cellular immune injury, a variety of cytokines, chemokines, adhesion molecules in myositis immune pathological process plays an important role. 4, infection factors. Many pathogenic microorganisms are considered to be the initiation factors of dermatomyositis, such as Mycobacterium tuberculosis, parvovirus, hepatitis C virus, Coxsackie virus, enterovirus, HIV, human T cell leukemia virus, some RNA viruses such as coxsackie virus, HIV has a pro-muscle.