Recurrent Remitting Seronegative Symmetrical Synovitis With Pitting Edema in a Nonagenarian: An Atypical Clinical Course Requiring Methotrexate for Remission.

Remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome is a rare inflammatory arthritis of older adults. We report a 92-year-old man who presented with fatigue and distal pitting edema, fulfilling the clinical features of RS3PE. Although corticosteroids are typically effective, he showed an incomplete response and relapsed despite dose escalation. Addition of methotrexate resulted in complete remission, with normalization of inflammatory markers. Elderly-onset rheumatoid arthritis and paraneoplastic RS3PE were considered but were clinically unlikely. This case highlights that RS3PE can occur even in nonagenarians and may require disease-modifying therapy when corticosteroid responsiveness is insufficient.