Remitting seronegative symmetrical synovitis with pitting edema syndrome with two different underlying malignancies: A case report.

Rationale: Remitting seronegative symmetric synovitis with pitting edema is a rare, benign disorder symmetrically affecting the peripheral joints. It begins with acute-onset pitting edema on the dorsum of the hands and feet, and primarily affects elderly men and has a favorable response to low-dose steroids. It may also be a paraneoplastic symptom of an underlying hidden cancer; hence, thorough clinical evaluation is required.

Patient concerns: A 58-year-old woman who presented with acute-onset polyarthritis and pitting edema affecting both hands and feet. Based on clinical and laboratory findings, remitting seronegative symmetric synovitis with pitting edema was diagnosed. A thorough clinical investigation led to a diagnosis of papillary thyroid carcinoma and adenocarcinoma of unknown origin.

Diagnoses: Based on clinical and laboratory findings, remitting seronegative symmetric synovitis with pitting edema was diagnosed. A thorough clinical investigation led to a diagnosis of papillary thyroid carcinoma and adenocarcinoma of unknown origin.

Interventions: The patient initially received prednisolone; when she faced difficulty in maintaining remission at a dose of <12.5 mg, hydroxychloroquine was added. Subsequently, the corticosteroid dose was tapered successfully without further arthritis flares. She also received palliative chemotherapy for an unknown primary.

Outcomes: Five rounds of chemotherapy successfully reduced the size of bilateral inguinal lymphadenopathy and garnered resolution of the small bilateral external iliac lymph nodes. Both corticosteroid and hydroxychloroquine discontinued. The patient remained stable and cancer-free at the 9-month follow-up.

Lessons: Physicians should be knowledgeable about the distinct signs and symptoms of remitting seronegative symmetric synovitis with pitting edema and investigate patients suspected of having the syndrome for hidden cancers.