[2] Caplan syndrome presents with cough and shortness of breath in conjunction with features of rheumatoid arthritis, such as painful joints and morning stiffness.

[3] The nodules in the lung typically occur bilaterally and peripherally, on a background of simple coal workers' pneumoconiosis.

Caplan syndrome occurs only in patients with both RA and pneumoconiosis related to mining dust (coal, asbestos, silica).

The presence of rheumatoid arthritis alters how a person's immune system responds to foreign materials, such as dust from a coal mine.

The syndrome is named after Dr. Anthony Caplan, a physician on the Cardiff Pneumoconiosis Panel, who identified the constellation of findings as a distinct entity in a 1953 publication.