A Case of Paraneoplastic Remitting Seronegative Symmetrical Synovitis with Pitting Edema Syndrome Improved by Chemotherapy.

The patient was a 69-year-old male who had started experiencing acute-onset pain in both shoulder joints and edema of both hands and feet. His symptoms progressively worsened within 1 month. Laboratory data indicated elevated CRP and erythrocyte sedimentation rate despite the normal range of antinuclear antibodies and rheumatoid factor and normal organ function. Furthermore, imaging data of the hand indicated synovitis without bone erosions. Meanwhile, chest CT revealed a lung tumor, leading to a diagnosis of primary lung adenocarcinoma with EGFR mutation (cT2aN3M0, stage IIIB). Based on these findings, he was diagnosed as suffering from paraneoplastic remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome. Thereafter, his symptoms disappeared as the tumor size was rapidly decreased by gefitinib therapy for lung adenocarcinoma. Currently, RS3PE syndrome can be classified as a vascular endothelial growth factor (VEGF)-associated disorder. Given that his symptoms improved by chemotherapy, the present case further supported the possible hypothesis that paraneoplastic RS3PE syndrome might be caused by tumor-induced VEGF. Therefore, the present case suggested that the symptoms of acute-onset joint pain accompanied by pitting edema in elderly patients should be considered suspicious for a malignant tumor, thereby warranting a detailed full-body examination.