Remitting seronegative symmetrical synovitis with pitting edema syndrome complicated with primary lung cancer.

Remitting seronegative symmetrical synovitis with pitting edema syndrome has been reported to be associated with malignant tumors. However, few cases occurring with lung cancer have been reported. We here report a case of remitting seronegative symmetrical synovitis with pitting edema syndrome complicated with lung cancer. A 77-year-old man presented with poly arthritis (both shoulders, knees, and hands), swelling of the hands, and an elevated C-reactive protein level. As the patient's rheumatoid factor was negative, he was diagnosed with remitting seronegative symmetrical synovitis with pitting edema syndrome. At the same time, computed tomography revealed a nodule suspicious of lung carcinoma in the right lower lobe. Right lower lobe lobectomy was performed, and the nodule was diagnosed as adenocarcinoma. Pathologically, pleural invasion and visceral pleural dissemination were detected, and the tumor was diagnosed as a primary lung carcinoma, p-T2aN0M1a, stage IV. During the preoperative interval, the remitting seronegative symmetrical synovitis with pitting edema syndrome had been successfully treated with prednisolone 20 mg/day, which was later reduced to 6 mg/day. Eighteen months after surgery, the patient's carcinoembryonic antigen levels increased, and the same symptoms recurred, this time more severely. We performed cranial magnetic resonance imaging and whole body positron emission tomography, but we did not detect any cancer recurrence. To treat the recurred remitting seronegative symmetrical synovitis with pitting edema syndrome, the patient has required not only prednisolone, but also azathioprine; however, the symptoms have not been controlled effectively. In our case, matrix metalloproteinase-3 levels were elevated, as shown in the tumor cells by immunohistochemistry. If higher matrix metalloproteinase-3 levels cause the symptoms, in our case, then remitting seronegative symmetrical synovitis syndrome might be considered a paraneoplastic syndrome. However, we could not conclusively determine if the subsequent reduction in matrix metalloproteinase-3 levels was the result of the surgery or the prednisolone treatment. Furthermore, based on the patient's progress following surgery, it is still not clear if the remitting seronegative symmetrical synovitis with pitting edema syndrome complicated with primary lung cancer in this case may be a paraneoplastic syndrome.