Remitting seronegative symmetrical synovitis with pitting edema

Remitting seronegative symmetrical synovitis with pitting edema (RS3PE) is a rare syndrome which is characterized by, as the name suggests, a seronegative symmetrical synovitis with pitting edema, most commonly affecting the hands, that rapidly remits with treatment.

Epidemiology

The exact incidence is unknown, but RS3PE is considered to be a rare rheumatological condition. The condition typically affects elderly men ^1-3.

Associations

RS3PE has been described as a paraneoplastic phenomena and in association with other rheumatological conditions (e.g. polymyalgia rheumatica, spondyloarthropathies) ^1-5.

Clinical presentation

The clinical presentation generally has an abrupt onset, with symmetric synovitis of the small hand joints, wrist, and extensor tendon sheaths, associated with pitting edema of the dorsum of the hands ^1,2. This gives the hands a classic 'boxing glove' appearance ⁶. Although classically affecting the hands, involvement of the feet and larger joints has also been reported, as has asymmetric joint involvement ^1,2. In most cases, RS3PE presents as a single episode and does not reoccur ^1,2.

Complications

• carpal tunnel syndrome ²

Pathology

The pathogenesis of RS3PE is not well understood. Notably, given its association with other rheumatological conditions, there is some conjecture regarding whether RS3PE is truly a standalone medical condition ^2,4.

Markers

Although traditionally thought to be seronegative, a term used in reference to rheumatoid factor (RF) ^1,2, matrix metalloproteinase-3 (MMP-3) has emerged as a potential positive serum marker in some patients, especially those where RS3PE is a paraneoplastic phenomena ^3,5. Additionally, general inflammatory markers such as CRP and ESR are often raised ³.

Radiographic features

Plain radiograph

Plain hand radiograph may show soft tissue swelling, but is otherwise typically normal if RS3PE is present in isolation, with no evidence of erosions or other bony changes ^2,6.

Ultrasound

Ultrasound, color Doppler ultrasound, and contrast‐enhanced Doppler ultrasound are all useful modalities, with the latter being the most sensitive ¹. Potential findings include:

• subcutaneous edema with hypoechoic dilation of lymphatics, more prominent in the dorsum of the hand ¹
• peritendinous hypoechoic thickening with hypervascularisation, more prominent in extensor tendons ¹

MRI

MRI of the hands is the more sensitive imaging modality of choice ^1,2, revealing:

• subcutaneous edema, more prominent in the dorsum of the hand, maximal in the mid-dorsum in one study ^1,2
• enhancement of tendon sheaths, more prominent in extensor tendon sheaths ^1,2
• small joint articular enhancement and effusions, most commonly affecting MCPs ^1,2

Treatment and prognosis

RS3PE typically rapidly remits following initiation of prednisolone ^1,2, often within one week. The response is slower with non-steroidal anti-inflammatory drugs (NSAIDs) ².

History and etymology

The condition was first described by Daniel J McCarty, an American rheumatologist, and his colleagues in their 1985 seminal case series ⁷.