Kidney disease and silicosis.

AIM: To determine the prevalence of kidney disease in a cohort of individuals with silicosis. METHODS: Review of medical records and questionnaires from patients reported to a state surveillance system for silicosis. Reporting of individuals with silicosis is required by state law. All individuals with silicosis reported as required by law to the State of Michigan. Individuals included in this article were reported from 1987 to 1995. Cases were reported by hospitals, physicians, the state workers' compensation bureau, or from death certificates. Only individuals who met the criteria for silicosis developed by the National Institute for Occupational Safety and Health (NIOSH) were included. RESULTS: Medical records were reviewed of 583 individuals with confirmed silicosis. This was mainly a population of elderly men. Ten percent of the 583 silicotics were found to have some mention of chronic kidney disease, and 33% of the 283 silicotics who we had laboratory tests on had a serum creatinine level >1.5 mg/dl. An association between kidney disease and age and between kidney disease and race was found among this cohort of 583 silicotics. Individuals with silicosis were more likely to have a serum creatinine level >1.5 mg/dl than age- and race-matched controls. However, no relationship between duration of exposure to silica or profusion of scarring on chest X-ray and prevalence of kidney disease or elevated creatinine levels was found. CONCLUSIONS: This study confirms previous case reports and epidemiologic studies of end-stage renal disease that found an association between kidney disease and exposure to silica. The epidemiologic data are conflicting on the mechanism by which silica causes kidney disease and are compatible with silica being able to cause kidney disease by both an autoimmune and direct nephrotoxic effect. Chronic kidney disease should be considered as a complication of silicosis.

Connective tissue disease and silicosis.

BACKGROUND: To determine the prevalence of connective tissue disease in a cohort of individuals with silicosis, we reviewed the medical records and questionnaires from individuals reported from 1987 to 1995 to a state surveillance system for silicosis. Reporting of individuals with silicosis is required by state law. Cases were reported by hospitals, physicians, the state workers' compensation bureau, or from death certificates. Only individuals who met the criteria for silicosis developed by the National Institute for Occupational Safety and Health (NIOSH) were included in the analysis. RESULTS: A questionnaire was completed for all 583 cases. Medical records were available for 463. There were 24 people with rheumatoid arthritis, one with scleroderma, and one with systemic lupus erythematosus. All were men. The prevalence of rheumatoid arthritis was 5.2% (relative risk (RR) 2.73, 95% confidence limit (CL) 1.75-4.06). The prevalence of scleroderma was 0.2% (RR 15.65, 95% CL 0.21-87.03) and the prevalence of systemic lupus erythematosus was 0.2% (RR 11.37, 95% CL 0.15-63.23). This is an approximately 2.5-15-fold increased risk for these connective tissue diseases compared to estimated prevalences in the general population. Individuals with silicosis and connective tissue disease did not differ from individuals with silicosis but without connective tissue disease by race, age, type of industry where exposed to silica, history of tuberculosis, whether or not they had applied for workers' compensation, and whether or not they had progressive massive fibrosis on chest x-ray. CONCLUSION: Although the association between scleroderma and silicosis has been more widely reported in the literature, the prevalence of rheumatoid arthritis was greater than the prevalence of scleroderma or systemic lupus erythematosus among a cohort of individuals with silicosis.