Author(s): Éric Toussirot [*] aff1 aff2 aff3
biological agents; IL-17; IL-23; spondyloarthritis; TNF[alpha] inhibitors
Spondyloarthritis (SpA) refers to an interrelated group of disorders that share a common genetic background, and clinical and radiological features [ 1 ]. This group was formerly divided into five subtypes, including ankylosing spondylitis (AS), psoriatic arthritis (PsA), inflammatory bowel disease (IBD) - associated arthritis, reactive arthritis and undifferentiated SpA. SpA mainly affects the axial skeleton, leading to erosions and osteoproliferative changes in the sacroiliac joints (SIJ) and/or the spine. The other clinical features of SpA are asymmetrical oligoarthritis, enthesitis, dactylitis and specific extraskeletal manifestations such as psoriasis, uveitis and chronic IBD. The approaches to the diagnosis, follow-up and management of SpA have undergone substantial changes over the last 10 years, especially with the development of new classification criteria [2 ]. AS is the prototype of the SpA group and is usually diagnosed using conventional pelvic x-ray examination, which shows bilateral sacroiliitis. Radiographic sacroiliitis is included in the modified New York criteria and is required for the diagnosis and classification of AS [3 ]. According to these criteria, the radiographic item is defined by the presence of bilateral sacroiliitis grade 2-3 or unilateral sacroiliitis grade 3-4. One major limitation of these criteria is that radiographic changes on SIJ may take several years to become detectable. Other sets of criteria have thus been developed for the recognition of patients with recent onset disease and other clinical forms of SpA. In addition, MRI has emerged as an important imaging tool for the early detection of acute inflammation of the SIJ and/or the spine in patients with SpA [4 ]. Thus, nonradiographic axial (Ax) SpA has been defined based on the absence of such radiographic changes of the SIJ, but in the presence of sacroiliitis as shown by MRI. In this regard, the Assessment of Spondyloarthritis International Society (ASAS) has proposed a set of criteria for the recognition of patients with early Ax SpA [5 ]. The patients covered by these criteria include those with radiographic Ax SpA (or AS) and also nonradiographic Ax SpA. Classification criteria have also been developed for peripheral SpA and thus, this novel approach to classification has differentiated two predominant manifestations of SpA, namely axial and/or peripheral disease [6 ]. However, clinical trials evaluating novel therapies in SpA, including biologics, have been performed mostly in patients with AS (and more recently, in those with nonradiographic Ax SpA). Thus, limited information is available regarding the effect of these treatments on peripheral disease manifestations [7 ]. In addition, the ASAS classification criteria for Ax SpA overlap with the classification of PsA for patients who have concomitant or familial history of psoriasis. PsA is a heterogeneous disease with several subtypes, and clinical trials designed in patients with PsA usually enrolled the polyarthritis form, which is not typical of SpA.
The management of SpA has considerably progressed over the last decade [ 7 ]. For a long time, therapeutics for the treatment of AS were limited to nonsteroidal anti-inflammatory drugs...