Silica exposure, silicosis, autoimmune diseases, tuberculosis and nontuberculous pulmonary mycobacterial disease

Introduction: Silica exposure is well stablished as the causal agent of silicosis as well as a risk factor for the development of systemic autoimmune diseases, especially rheumatoid arthritis (RA), systemic sclerosis (SSc) and systemic lupus erythematosus (SLE). Silica exposure is also related to tuberculosis (TB) and nontuberculous pulmonary mycobacterial (NTM) infections. Additionally, patients with autoimmune diseases have increased risk of TB. Aims: To analyze our database of patients with silica exposure and systemic autoimmune diseases and the development of TB and NTM. Methods: We describe the findings of 22 consecutive patients attending our service with silicosis and systemic autoimmune diseases. Results: The average age at diagnosis of silicosis was 49.9 ± 9.9 years old. The mean duration of silica exposure was 16.5 ± 10.8 years and the mean time to diagnosis after initial exposure was 26.0 ± 12.8 years. The occupational exposures of these patients were stone cutting (36%), sandblasting (27%), silica artifacts manufacturing (18%), stone finishing (13%), foundry working (9%) and well drilling (4%). Eight (36%) patients were diagnosed with RA, 7 (32%) with SSc, 4 (18%) with undifferentiated connective tissue disease, 2 (9%) with SLE, 1 (4%) with Sjogren9s syndrome. Four (18%) patients received the diagnosis of TB and 4 (18%) of NTM. Conclusion: It called our attention that 36% of our patients with silicosis and systemic autoimmune diseases developed TB or NTM. These findings reinforce the need to prevent silica exposure as well as to carefully investigate latent or active TB and NTM infections before starting immunosuppressive drugs on these patients.