Table 2.

Systemic autoimmune diseases (SADs) and their characteristics.

Disease	Genetics	Environmental factors
Mixed connective tissue disease (MCTD)	HLA-DRB1, multiple genes	VitD, smoking, EBV, sunburn, silica dust
Polymyositis – dermatomyositis (PM-DM)	HLA-DRB1, multiple genes	Smoking
Rheumatoid arthritis (RA)	HLA-DRB1, PTPN22, multiple genes	VitD, smoking, EBV
Sjögren’s syndrome (SS)	HLA-DRB1, PTPN22, multiple genes	VitD, EBV, inverse correlation with smoking
Systemic lupus erythematosus (SLE)	HLA-DRB1, C’, multiple genes	VitD, smoking, EBV, sunburn, silica dust
Systemic sclerosis (SSc) HLA-DRB1, multiple genes Silica dust, solvents