Rituximab is a chimeric human/mouse monoclonal anti-CD20 antibody approved for the treatment of rheumatoid arthritis (RA) refractory to anti-tumour necrosis factor (TNF) therapy.1 Rituximab seems to be efficient in other diseases such as autoimmune cytopoenia,2 systemic lupus erythaematosus (SLE),3 dermatomyositis4 and Sjögren syndrome.5 To our knowledge, no case of psoriatic arthritis (PsA) treated by rituximab has been reported. Nevertheless, a partial remission of psoriasis following rituximab therapy for non-Hodgkin’s lymphoma has been reported.6 We describe the case of a man with severe PsA with dramatic improvement after rituximab treatment.

A 62-year-old Caucasian male had PsA since 2001 with asymmetrical arthritis involving distal interphalangeal arthritis, wrist, knee and ankle joint, and dactylitis. He has a personal (15 years ago) and familial history of psoriasis. Antibodies to cyclic citrullinated peptide (CCP) and rheumatoid factor (RF) were negative, human leukocyte antigen (HLA) typing gave HLA A1 A24 B7 B8 DRB1*03 DRB1*15 DQB1*02 DQB1*06. The initial radiographs in October 2001 of the hands (fig 1A) and feet showed small erosions on the third interphalangeal distal bilateral joints, first left metacarpophalangeal and first left metatarsophalangeal joints. Follow-up radiographs showed progression 3 years later (fig 1B). The patient was refractory to methotrexate (MTX). He had inadequate response to biologicals (each time associated with MTX) including anakinra for 1 year and etanercept for 7 months. Subsequently we proposed infliximab, but after the first infusion the patient developed endocarditis and septicaemia with Staphylococcus aureus as a result of dental work, leading to infliximab withdrawal. Because of persistence of the inflammatory symptoms (presence of seven swollen and eight tender joints, morning stiffness lasting 15 min), with erythrocyte sedimentation rate (ESR) 6 mm/h and C-reactive protein (CRP) 18 mg/dl, the patient was given four rituximab infusions (375 mg/m2 intravenously) at 4-week intervals, associated with prednisone 10 mg daily. At 3 months later, a dramatic improvement was observed with persistence of seven (probably chronic) swollen joints but no tender joints, absence of morning stiffness, ESR 5 mm/h and CRP 12 mg/dl. At 4 months later, to maintain this improvement, MTX 10 mg weekly was added then increased gradually to 25 mg with variation in the dosage for 2 years related to digestive intolerance. At 8 months (September 2004), the patient relapsed with six swollen and tender joints, morning stiffness lasting 30 min, ESR 11 mm/h and CRP 30 mg/dl, and was treated again (1000 mg infusion) with sustained response. In April 2005, the patient had an arthrodesis of the right radiocarpal joint. At last follow-up in December 2006, the patient was still on MTX associated with prednisone (10 mg daily). The disease was controlled (four swollen and five tender joints, morning stiffness lasting 15 min, ESR 6 mm/h and CRP 8 mg/dl) without relapse and need for re-treatment. Radiographs (fig 1C) did not show progression compared to the 2004 radiographs.

• Download figure
• Open in new tab
• Download powerpoint

Figure 1 Initial radiographs of the hands show discrete erosions (A) then progression over 3 years with erosive interphalangeal distal and proximal joints with juxtaarticular new bone formation at multiples sites, first left metacarpophalangeal joint, wrists, carps and bilateral radiocubital inferior joints (B) and, finally, apparent absence of progression after 5 years (C).

The clinical, immunological and radiological features of our patient were characteristic for PsA and, according to the CASPAR (for “classification criteria for psoriatic arthritis”) criteria,7 the diagnosis was established. The diagnosis of RA was excluded regarding clinical and radiological characteristics, and negative tests for anti-CCP, RF and absence of HLA-DRB1*04. The efficacy of rituximab, associated with MTX, on joint inflammation in our case suggests a role of B cells in PsA. This is supported by a recent study8 having highlighted the presence of B cell lymphoid aggregates in PsA synovial tissues. This is an original report of PsA treated with rituximab with an analysis of radiographic evolution over 3 years, suggesting a possible structural effect in this case. Obviously, studies to confirm the clinical and radiological efficacy on arthritis and efficacy on skin lesions of rituximab in PsA are warranted.