RS3PE and the role of ultrasound. A case report and brief review of the literature

Remitting seronegative symmetric synovitis with pitting edema (RS3PE) is a rare syndrome characterised by acute onset of symmetrical distal synovitis and tenosynovitis, associated with severe pitting edema of the dorsum of the hands and feet, seronegativity for autoimmunity and dramatic response to glucocorticoids. First described by McCarty et al. in 1985, RS3PE is reported mostly in elderly males, but it can also rarely occur in young people. Although it was initially regarded as a form of rheumatoid arthritis (RA), it is now considered a clinical distinct entity that can be associated with other rheumatologic conditions or be secondary to underlying diseases, such as cancer. As revealed by magnetic resonance imaging (MRI), the typical landmark of RS3PE is extensor tenosynovitis. Due to extensive subcutaneous edema of the extremities, the clinical assessment of synovitis and tenosynovitis is difficult. On the other hand, the use of MRI is expensive, time-consuming and requires experienced staffs. Musculoskeletal ultrasound (MSUS) may be a viable, reliable and cost-effective tool for evaluation of RS3PE patients. We hereby report the case of an 84 year-old woman presenting with bilateral hand and wrist swelling and morning stiffness. Clinical examination, laboratory tests and imaging led to a diagnosis of RS3PE. The aim of this report is to discuss the role of MSUS in RS3PE for the purpose of diagnosis and differential diagnosis compared with other rheumatologic conditions.