Polyarthritis as a prewarning sign of occult lung cancer

Cancer polyarthritis is an uncommon, paraneoplastic manifestation of some solid and hematological malignancies. Herein, we report the case of a 55-year-old woman who recently experienced polyarthritis for 2 months. On admission, the patient developed cough, expectoration, and fever. According to the clinical manifestations and the findings in radiological examinations and sputum cultures, pneumonia was considered. No evidence of lung cancer was noted by repeated computed tomography scan of lung, single bronchoscopy, or computed tomography-guided lung biopsy. Ultimately, the second bronchoscopy with biopsy was carried out, and lung adenocarcinoma was confirmed by pathological examination. Symptoms of polyarthritis starting 2 months before the symptoms of her lung cancer in the present case leads us to believe that polyarthritis may be a manifestation of paraneoplastic syndrome. Arthritis resolved after anticancer therapy. Our report indicates that polyarthritis of unknown cause may be suspected as a manifestation of malignancies.