Caplan syndrome

Last revised by Yoshi Yu on 1 Jun 2024

Caplan syndrome, also known as rheumatoid pneumoconiosis, is the combination of seropositive rheumatoid arthritis and pneumoconiosis.

Although first described in coal miners (coal workers' pneumoconiosis), it has subsequently been found in a variety of other pneumoconioses 2

Affects 2-6% of patients with pneumoconiosis in Wales 4, while another study reported 11-18% in China 6. The association between rheumatoid arthritis and silicosis is stronger in the presence of progressive massive fibrosis, compared with simple silicosis 6.

Little data exists on how the presence of rheumatoid arthritis affects the severity of pneumoconiosis or vice versa. However, a 2021 study suggests that the presence of silica exposure increases the severity of rheumatoid arthritis 6.

An established association exists between occupational dust exposure and the development of autoimmune diseases 6. It is postulated that inhaled dust particles, which are engulfed by alveolar macrophages triggers chronic inflammation, immune activation and fibrosis, eventually leading to autoantibody production in genetically susceptible individuals 6.

As opposed to necrobiotic nodules in simple rheumatoid arthritis, in Caplan syndrome, a dust ring with inflammatory cells (granulocytes, macrophages and giant cells) surrounds the necrotic core 4-6. Dust can sometimes be identified in the necrotic core and within macrophages 6.

  • 5-50 mm well-defined nodules in the upper lung lobes/lung periphery

  • nodules may remain unchanged, multiply, calcify, or become thick walled cavities

  • background changes of pneumoconiosis

  • may have an accompanying pleural effusion

  • features often grow in short bursts

It was first described by A Caplan in 1953 1.

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