A systematic comparison of rheumatoid arthritis and ankylosing spondylitis: structural outcomes.

Rheumatoid arthritis and ankylosing spondylitis are both chronic diseases with inflammation as a hallmark. Both diseases are characterized by structural abnormalities of the peripheral joints (RA) or the spine (AS) that can be visualized on conventional radiographs. RA is associated with destruction (erosions, joint space narrowing) whilst AS is dominated by bone formation (syndesmophytes). The causative relationship between inflammation and structural damage in RA is well established, whilst this relation is largely unknown but certainly less strong in AS. Progression of structural damage in RA is inhibited by disease modifying anti-rheumatic drugs and especially by TNF-blockade, whilst progression of structural damage in AS seems insensitive to TNF-blockade but sensitive to non-steroidal inflammatory drugs.In this article, similarities and dissimilarities with respect to structural damage in RA and AS are discussed and set against a background.