Treatment of Refractory Psoriatic Arthritis with Infliximab: a 12 Month Observational Study of 16 Patients

Objective: To evaluate the effectiveness and toxicity of infliximab in patients with recalcitrant psoriatic arthritis (PsA).

Methods: Patients with treatment resistant PsA and at least six actively inflamed joints, who had failed to respond to at least two disease modifying agents, were included. Infliximab (5 mg/kg) was given at weeks 0, 2, 6, and every 6-8 weeks pending response. Clinical and laboratory measures included actively inflamed joint count (AJC), swollen joint count (SJC), psoriasis severity (PASI), HAQ, and SF-36. Response was defined as at least a 30% reduction in AJC and PASI. Differences from baseline were analysed using the signed rank test.

Results: Sixteen patients (12 male, 4 female), mean age 48 and disease duration 14 years, were included. At baseline the mean AJC was 22.5 and mean PASI 4.5. Eleven patients continued receiving methotrexate. The AJC did not show a statistically significant response. SJC improved significantly at week 54 (p = 0.01). The PASI improved significantly at weeks 14 (p = 0.001) and 30 (p = 0.002) and CRP was reduced significantly at week 30 (p = 0.02). The HAQ score improved at week 30 (p = 0.02). Six patients became positive for dsDNA without clinical features of a connective tissue disease. Six patients discontinued treatment owing to lack of efficacy (1) and toxicity (5). Other serious adverse events included: urticaria (3); thrombocytopenia (1); lower gastrointestinal bleeding (2); severe diarrhoea (2); serious infections (6). Raised transaminases, at least 1.5x normal, occurred in four patients.

Conclusion: In refractory PsA, infliximab led to a marked improvement in psoriasis but modest response in joint disease. Toxicity and rate of treatment termination was high.