A case report of extra-articular manifestation of rheumatoid arthritis: Rheumatoid nodules in lungs.

Rheumatoid arthritis is a systemic inflammatory disorder primarily affecting joints but not limited to the joints alone. Extra-articular manifestations involve skin, ocular, gastrointestinal, pulmonary, cardiac, renal, neurological, and hematological systems. Among them, skin manifestations (20%) are most common, presenting as nodules on the extensor surfaces of the upper and lower extremities. In rare cases these nodules can also be detected within the heart and lungs. Interestingly, rheumatoid nodules are often seen in patients on leflunomide, methotrexate, or tumor necrosis factor-alpha antagonists. Nevertheless, definitive diagnosis requires a histopathological analysis. In this case report, we presented a 49-year-old male patient with a relatively short period of disease activity leading to rheumatoid nodules in the lungs. Considering the ongoing COVID-19 pandemic and that tuberculosis was still endemic in Kazakhstan, achieving the definite diagnosis was challenging. Initial imaging study revealed bilateral polysegmental pneumonia. The tests for COVID-19 and pulmonary tuberculosis were negative. A follow-up chest computed tomography scan had signs of disseminated lung lesions of unknown origin. Lung biopsy showed a morphological picture of productive granulomas characteristic for tuberculosis. However, at the second look, typical scarring granulomas typically seen in rheumatoid nodules were observed.