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Caplan Syndrome — SCE Rheumatology MCQ

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HardRheumatoid ArthritisCaplan SyndromeSCE Rheumatology

A 50-year-old man with seropositive rheumatoid arthritis worked underground as a coal miner for 25 years. Surveillance imaging shows mild simple coal workers' pneumoconiosis. Serial chest radiographs then demonstrate the relatively rapid appearance, in crops, of multiple sharply marginated round nodules measuring 0.5–4 cm. On CT, the nodules are predominantly peripheral and several have cavitated. He has no fever or constitutional symptoms. What is the most likely diagnosis?

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Correct answer: E — Caplan syndrome (rheumatoid pneumoconiosis)

The diagnosis is Caplan syndrome, or rheumatoid pneumoconiosis. Its defining pattern is rheumatoid arthritis in a person exposed to inorganic occupational dust, classically a coal miner, with multiple sharply defined rounded pulmonary nodules. The nodules are often peripheral, may appear rapidly in crops, and can cavitate or calcify. They commonly occur with only mild background pneumoconiosis, as in this case. Progressive massive fibrosis more typically produces large confluent upper-lobe fibrotic masses with architectural distortion rather than crops of discrete peripheral nodules. Rheumatoid pulmonary nodules can occur without dust exposure, but this characteristic occupational association warrants the specific diagnosis of Caplan syndrome. Methotrexate pneumonitis usually causes an acute or subacute diffuse interstitial or ground-glass pattern. Nodular sarcoidosis would not explain the highly characteristic rheumatoid–coal-dust association.

Reference: Schreiber J, Koschel D, Kekow J, et al. Rheumatoid pneumoconiosis (Caplan's syndrome). European Journal of Internal Medicine. 2010;21(3):168–172. https://pubmed.ncbi.nlm.nih.gov/20493416/