Rheumatoid arthritis (RA) has been associated with silicosis in a number of studies. [Rom, p. 379] "Although RA involves autoimmune reactions, the precise cause is unknown; many factors may contribute." Unknown factors (e.g., viral infections) are thought to play a role. [Merck Manual, p. 303] RA is 2-3 times more prevalent in women than in men. "Despite the absence of clear evidence linking any infectious agent to RA, it is widely believed that ultimately an important triggering role will be elucidated for infectious or other environmental agents." [Cecil, 24th Ed, p. 1682-3] 1,022 cases of silicosis were reported in the state of Michigan between 1985 to 2006, Medical records were available for 790 of these cases and showed a diagnosis of rheumatoid arthritis in 33 (a prevalence ratio of 2.26, or 6.96, depending upon the reference rate used). [
PMID 20957678] In a study of autoimmune disease mortality in 26 US states and occupational exposures, no increased risk of RA was found for those in jobs likely to include silica exposure. [
PMID 17907164] Silicosis affects the immune system; patients have increased susceptibility to tuberculosis and some fungal infections. [LaDou, p. 379]