Rheumatic conditions (prevalence)
Rheumatoid arthritis (50 to 90%)
Systemic lupus erythematosus (15 to 35%)
Sjögren's syndrome (75 to 95%)
Systemic sclerosis (20 to 30%)
Cryoglobulinemia (40 to 100%)
Mixed connective tissue disease (50 to 60%)
Nonrheumatic conditions
Aging
Infection: bacterial endocarditis, liver disease, tuberculosis, syphilis, viral infections (especially mumps, rubella and influenza), parasitic diseases
Pulmonary disease: sarcoidosis, interstitial pulmonary fibrosis, silicosis, asbestosis
Miscellaneous diseases: primary biliary cirrhosis, malignancy (especially leukemia and colon cancer)