Seropositive, symmetric polyarthritis in a patient with poorly differentiated lung carcinoma: carcinomatous polyarthritis, hypertrophic osteoarthropathy, or rheumatoid arthritis?

Polyarthritis resembling rheumatoid arthritis (RA) may be the presenting manifestation of occult malignancy. Hypertrophic osteoarthropathy (HOA) may also develop in association with pulmonary neoplasia and consists of clubbing, periostitis, and arthropathy. We describe a patient who presented with a seropositive, symmetric, inflammatory polyarthritis only 4 weeks before a lung tumor became clinically and radiographically apparent. After initiation of chemotherapy, she developed features characteristic of HOA. It appears that the patient had both RA and HOA. We discuss the differential diagnosis and review the relationship of RA, HOA, carcinomatous polyarthritis, and malignancy.