Extra-articular manifestations of ankylosing spondylitis: Prevalence, characteristics and therapeutic implications

Ankylosing spondylitis (AS) is the most frequent and most severe subtype of spondyloarthritis and can be an outcome of any of the other spondyloarthritis subtypes. It primarily affects the axial joints, most notably the sacroiliac joints. Other sites of involvement include the spine, peripheral joints, and entheses (capsules, ligaments, and tendons). Inflammatory enthesopathy progressing to ossification and ankylosis is the pathologic basis for the disease. Extra-articular manifestations vary widely in terms of both frequency and severity. The most common extra-articular manifestations are represented by uveitis, bowel disease, heart, lung, skin, bone and kidney involvement. This review focuses on prevalence and clinical characteristics of the most common extra-articular manifestations in AS, and discuss the diagnosis and therapeutic difficulties that rheumatologists faces when dealing with such manifestations. The advantages of treatment with non-steroidal anti-inflammatory drugs (NSAIDs), especially if continuous use is envisaged, should be weighted against possible gastrointestinal and cardiovascular disadvantages. In the presence of history of gastrointestinal complaints or a high cardiovascular risk, NSAIDs should be used with caution. TNF inhibition has demonstrated effectiveness in the treatment of AS symptoms and all currently available anti-TNF agents appear to have similar efficacy. However, the efficacy of anti-TNF agents varies in the presence of extra-articular manifestations. Etanercept appears to have very little effect on inflammatory bowel disease and limited efficacy on the course of uveitis probably inferior to the monoclonal antibodies infliximab and adalimumab.