RELATIONSHIP BETWEEN AUTOIMMUNE DISEASES AND PNEUMOCONIOSIS

In recent years, with the aging of patients with pneumoconiosis, autoimmune diseases as a complication have been observed. One of the reasons for this may be that autoimmune diseases are prone to develop among the elderly. On the other hand, it has been reported that dust itself, such as silica for example, has adjuvant effect. A review of the recent literature published in Japan and abroad was made to clarify the relationship between pneumoconiosis and autoimmune diseases and the following results were obtained. 1) Disorders which accompany pneumoconiosis: Scleroderma, rheumatoid arthritis, systemic lupus erythematosus (SLE), and disorders of the kidney and liver have been reported. In Japan, about 30 cases of pneumoconiosis accompanied with autoimmune diseases have been reported. In many of the reports, patients with pneumoconiosis and scleroderma have a past history of exposure to silica. In both case studies and case control studies, patients with rheumatoid arthritis and history of silica exposure are prone to develop pnemoconiosis. 2) Immunological studies of patients with pneumoconiosis: As for humoral immunity, elevation of polyclonal γ-globulin, especially IgG, has been often reported together with high positive rate of autoantibodies such as antinuclear antibodies. In cellular immunity, decreased delayed type skin reaction and decreased CD4/8 ratio have been reported. In human leukocyte antigen (HLA) typing the elevated frequency of DR4 has been reported. In the study of BAL increased production of superoxide anion O2- by alveolar macrophages has been observed. 3) Experimental studies: Silica is well known for its toxicity to cells and also for its adjuvant effect. In the German Democratic Republic, patients with scleroderma and history of long term silica exposure are recognized as patients with occupational disease even though pneumoconiosis is not clearly demonstrated on X-ray film. It is defficult from this review to nrake a definite conclusion regarding the relation between silicosis and autoimmune diseases. There is a need to repeat this review of the literature on autoimmune diseases and pneumoconiosis in the near future.