Diffuse large B-cell lymphoma with lung involvement in a psoriatic arthritis patient treated with methotrexate.

Non-Hodgkin lymphoma (NHL) occurs in the setting of methotrexate (MTX) therapy for rheumatoid arthritis. However, it has been very rarely reported in subjects with psoriatic arthritis treated with MTX. We report here a case of a 70-year-old woman with psoriatic arthritis who presented with bilateral lung infiltrates, pleural effusion, splenomegaly, and inguinal lymphadenopathy during treatment with MTX. The diagnosis of diffuse large B-cell lymphoma was made by analysis of the pleural fluid via thoracentesis and biopsy of an enlarged inguinal lymph node. Clinicians should consider the possibility of a NHL complicating psoriasis and with MTX therapy in order to prevent treatment delays.