[Arthritis and pulmonary cavities].

This case report describes the very rare simultaneous occurrence of rheumatoid arthritis and granulomatosis with polyangiitis with the only organ manifestation of life-threatening bilateral pulmonary cavities. Due to the acuteness of the vasculitis, treatment was primarily with cyclophosphamide infusions and high-dose glucocorticoids, and in the further course with high-dose methotrexate. Routine thoracic imaging also seems to be useful when conventional basic rheumatologic treatment is newly initiated, as treatment-decisive changes are seen with a relevant frequency. The occurrence of both autoimmune diseases might be due to common genetic predispositions.