Caplan syndrome refers to rheumatoid arthritis occurring with which condition?

• A. Osteoarthritis
• B. Pneumoconiosis (e.g., silicosis or coal workers' pneumoconiosis)
• C. Psoriatic arthritis
• D. Ankylosing spondylitis

Answer: (B)

Caplan syndrome is the combination of rheumatoid arthritis with pneumoconiosis, typically in people exposed to coal dust or silica. The hallmark is the development of multiple, well-defined rheumatoid nodules in the lungs on imaging, in the setting of dust-related lung disease. This distinct association arises when autoimmune RA coexists with pneumoconiosis, leading to these lung nodules that can be seen on chest radiographs or CT. Other arthritides like osteoarthritis, psoriatic arthritis, or ankylosing spondylitis do not involve this dust-related lung process, so they don’t define Caplan syndrome.