Synchronous Occurrence of Bazex Syndrome and Remitting Seronegative Symmetrical Synovitis with Pitting Edema Syndrome in a Patient with Lung Cancer

A 69-year-old man developed bilateral polyarthritis, edematous extremities, and skin desquamation on the fingers and ears. He did not meet the criteria for any connective tissue disease, including rheumatoid arthritis. An examination revealed advanced lung cancer. His systemic manifestations were attributed to paraneoplastic Bazex syndrome and remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome. Treatment with pembrolizumab (an anti-programmed death-1 antibody) for lung cancer relieved his symptoms and shrank the lung tumor. Bazex and RS3PE syndromes are rare paraneoplastic diseases. We herein report this unique case of synchronous development of these two paraneoplastic syndromes in the presence of advanced lung cancer.