Rheumatoid pneumoconiosis (Caplan's Syndrome)

High resolution CT of 84 year old man with rheumatoid arthritis. a) Mediastinal window image showing cavitatory lesions in bilateral upper lobes (arrows) with large fibrotic area in right upper lobe (arrow head) and few subpleural fibrotic lesions (arrows in image [b]) in left upper lobe. c) High resolution CT scan lung window shows multiple diffuse reticulonodular lesions in bilateral lungs these features suggestive of pneumoconiosis with progressive massive fibrosis (PMF).

It is also known as Caplan's Syndrome, associated with coal worker's pneumoconiosis and silicosis. The incidence is falling as the coal mining industry has been in decline. Chest radiograph shows multiple, well defined, rounded opacities, 0.5 to 5 cm in diameter distributed throughout the lungs with or without eggshell calcification of hilar lymph nodes. HRCT findings include small nodules with perilymphatic distribution associated with necrobiotic nodules demonstrating cavitation, which are indistinguishable from tubercular cavity. The active inflammatory zone around the rheumatoid pneumoconiotic nodules distinguishes from nonrheumatoid pneumoconiotic nodules. Progressive massive fibrosis (PMF) is irregularly outlined few soft tissue nodules with surrounding fibrosis in apical regions, more often seen with simple pneumoconiosis than Caplan’s syndrome.