<prompt> Caplans syndrome of rheumatoid arthritis with pneumoconiosis is characterized byLung nodules and diffuse pulmonary fibrosisBilateral symmetrical lung cavitations with pulmonary fibrosis.Air-space consolidation with patchy pulmonary fibrosis.Interstitial pneumonitis with hilar adenopathy.  <response>: Ans. a Lung nodules and diffuse pulmonary fibrosis. Ref. Harrison, Medicine, 16th ed., 1524CAPLANS SYNDROME Caplans syndrome is characterized by triad of- Pulmonary nodules,- Pneumoconiosis progressive massive fibrosis, andin- Rheumatoid disease seropositive. The immuno-pathological mechanism involves:- Direct cytotoxicity of inorganic dust- Stimulation of reactive oxygen- Activation of macrophages to produce cytokines and TNF alpha fibrogenic factor- Increased protease activity- Increased activation of alpha 1 antitrypsin and leucocyte elastase activity. 