Treatment of rheumatoid arthritis and ankylosing spondylitis

The treatment of the two most frequent inflammatory rheumatic diseases rheumatoid arthritis (RA) and ankylosing spondylitis (AS) has some similarities but in total more differences. Thus, therapy with non-steroidal anti-inflammatory agents (NSAIDs), conventional disease modifying anti-rheumatic drugs (DMARDs) and biologic agents has a different role in the management and different efficacy in AS and RA. This implies signs and symptoms, function, and structural damage. This is in part due to the different pathogenesis: (i) while the synovium is an important target in RA it is rather the bone in AS and (ii) while the pathology in RA is rather osteodestructive to cartilage and bone presenting with erosions, it is predominantly osteoproliferative in AS as indicated by syndesmophytes and ankylosis. Biologic agents targeting tumor necrosis factor (TNF-alpha) work clinically well in both diseases but, while they clearly inhibit structural damage in RA, they do not seem to have much influence on new bone formation in AS. DMARDs are efficacious in RA but less so in AS. NSAIDs are efficacious in both RA and AS, but they are considered first line of therapy in AS while they are rather adjunctive agents in RA. In AS, NSAIDs, potentially especially coxibs, may even prevent new bone formation due to their inhibitory effect on cyclooxygenase-2.