This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology and Rheumatology, Subject name: Medicine
[{'content': "Caplan's syndrome of rheumatoid arthritis with pneumoconiosis is characterized by \nSelect and explain. \nA. Lung nodules and diffuse pulmonary fibrosis, B. Bilateral symmetrical lung cavitations with pulmonary fibrosis., C. Air-space consolidation with patchy pulmonary fibrosis., D. Interstitial pneumonitis with hilar adenopathy.", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. a (Lung nodules and diffuse pulmonary fibrosis). (Ref. Harrison, Medicine, 16th ed., 1524)CAPLAN'S SYNDROME# Caplan's syndrome is characterized by triad of- Pulmonary nodules,- Pneumoconiosis (progressive massive fibrosis), and/in- 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.", 'role': 'assistant'}]