Which among the following is true about Caplan's syndrome?

Caplan's syndrome also known as rheumatoid pneumoconiosis or rheumatoid lung. It occurs in patients with both rheumatoid ahritis (usually seropositive patients) and pneumoconiosis related to mining dust (coal, asbestos, and silica) exposure and consists of multiple rounded nodules in the lung. Ref: Harrison's 17th ed chapter 314 ; Rheumatology and Immunology Therapy: A to Z Essentials edited by Larry W. Moreland, 2004, Page 186.