Unilateral RS3PE in a Patient of Seronegative Rheumatoid Arthritis

Remitting seronegative symmetrical synovitis with pitting edema (RS3PE) is a rare but well-reported clinical entity. It is classically described as symmetrical involvement of both upper extremities. Asymmetrical involvement had also been reported, but unilateral presentation is very rare. We hereby report a case of unilateral RS3PE in a patient of seronegative rheumatoid arthritis which was initially misdiagnosed as cellulitis and was given high dose antibiotics without any significant improvement. Later a rheumatologic consultation leads to a prompt diagnosis, and treatment with steroids leads to dramatic reversal of symptoms. This case demonstrates the rare presentation of this rare clinical entity and highlights the necessity of awareness regarding unilateral disease to clinicians. 1. Introduction Ever since remitting seronegative symmetrical synovitis with pitting edema was described by McCarty et al. [1] in 1985 as a subset of elderly onset rheumatoid arthritis, it has always drawn attention of rheumatologists with its distinct and varied clinical features. RS3PE is characterized by acute onset symmetrical polyarthritis with dramatic onset of pitting edema with extreme tenderness. The other peculiar features include male predominance, old age, negative rheumatoid factor, absence of bony erosions on radiographs, good response to low-dose steroids, and long-term remission after withdrawal of steroids. In all ten original cases described by McCarty the disease was bilaterally symmetrical. Since McCarty’s original description over 150 cases of RS3PE has been reported [2]. In almost all the cases it is described as a symmetrical disease involving both hands and rarely the feet [3]. Thus symmetrical presentation is considered as one of the hallmark of disease. However exceptions are always there. RS3PE too presents in an asymmetrical and unilateral pattern, though it is extremely rare. Thus diagnosing it always poses a clinical challenge, and correct diagnosis is delayed often. We hereby report a case of seronegative rheumatoid arthritis patient who developed acute onset polyarthritis with dramatic onset of pitting edema in left hand and was misdiagnosed to have cellulitis initially, but later a diagnosis of RS3PE was made, and she improved after a course of low-dose prednisolone. 2. Case Report A 68-year-old female, housewife, suffering from multiple peripheral joint pain along with morning stiffness was diagnosed having seronegative rheumatoid arthritis two years back and was given methotrexate (15？mg weekly) and leflunomide (10？mg daily) as per local