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Psoriatic arthritis (PsA) affects about 30% of patients with psoriasis and is a chronic inflammatory rheumatic disease, with the development of erosive and deforming arthritis in about 40% of patients.1 Tumour necrosis factor α (TNFα) has an established role in the pathogenesis of PsA, and the TNFα receptor blocker etanercept has been approved for its treatment.2
METHODS AND RESULTS
We evaluated in an open label, 2 year study the safety and efficacy of infliximab in association with methotrexate for patients with severe PsA. This study was an extension protocol of an initial 6 month study.7
Four men and eight women with PsA and active disease despite treatment with methotrexate + steroid + non-steroidal anti-inflammatory drugs had been enrolled and treated with five infusions of infliximab (Remicade, Centocor) at a dose of 5 mg/kg at weeks 0, 2, 6, 14, and 22. Thereafter the patients continued treatment with 5 mg/kg every 6 or 8 weeks for up to 2 years.
The patients had a mean (SD) age of 48.4 (13.6) years and a mean duration of articular symptoms of 8.6 (5.6) years. Eleven of the 12 patients had a polyarticular pattern of disease with predominantly peripheral arthritis. Two patients had been withdrawn from the study before the fifth infusion owing to the occurrence of severe diseases and another patient had to stop infliximab after the seventh infusion owing to a lymphadenitis due to cytomegalovirus. Nine patients continued infliximab treatment for up to 2 years.
The following outcome measures were evaluated: patient evaluation of global health status (100 mm visual analogue scale (VAS)); patient global assessment of disease activity (100 mm VAS); patient assessment of pain (100 mm VAS); Health Assessment Questionnaire (HAQ) scores; physician global assessment of disease activity (100 mm VAS); tender joint count; swollen joint count; erythrocyte sedimentation rate (ESR); C reactive protein level (CRP); Psoriasis Area and Severity Index (PASI).
The American College of Rheumatology (ACR) improvement criteria for rheumatoid arthritis with 20%, 50%, and 70% improvement were also assessed.
Radiographs of the hands and wrists were obtained at baseline and at 2 years for the patients with peripheral polyarthritis completing 2 years of infliximab treatment and were scored according to the modified Sharp’s method.8
At week 26 a significant decrease (p⩽0.05, by t test for paired data) had been seen for all variables, with the exception of ESR. At 1 and 2 years a significant decrease was maintained for all the outcome measures, with the persisting exception of ESR (table 1). Seven patients had received infliximab every 8 weeks, two of them every 6 weeks owing to a partial loss of efficacy.
At 1 year, 8/9 (89%) patients met the ACR20 and 6/9 (67%) patients the ACR70. At 2 years 9/9 (100%) patients met the ACR20 and 5/9 (56%) patients the ACR70.
Eight of nine patients completing 2 years of infliximab treatment had a predominantly peripheral polyarthritis. In these eight patients we did not observe a significant increase of radiographic Sharp’s score from baseline (table 2). In 5/8 (63%) patients we did not see any increase in Sharp’s score at the end of 2 years of infliximab treatment.
Our data suggest that long term treatment with infliximab may be highly effective for patients with severe PsA. These results are in partial contrast with those from another observational study,6 but similar to other recent observations.9 TNFα neutralising agents are being used by an increasing number of patients with PsA and the Italian Society of Rheumatology has recently published specific guidelines for their appropriate use.10
PsA is a heterogeneous disease and we need larger studies and more data to better select patients with PsA who may benefit from anti-TNFα treatment.