Several studies reported the predominant presence of CD8+ T cells in the muscles of patients with polymyositis and the presence of CD4+ T cells and complement deposition in the muscles of patients with dermatomyositis, suggesting that muscle tissue damage by CD8+ T cells as a mechanism of polymyositis and autoantibody-mediated vascular damage in muscle as a mechanism of dermatomyositis [8–10]. This evidence concerns the gene CD4 and polymyositis.