Page 113 - Recognizing axial spondyloarthritis - Janneke de Winter

INTRODUCTION
A major feature of spondyloarthritis (SpA) is its insidious onset and slow progression of signs, symptoms, and structural damage (1). This leads to a significant diagnostic delay of 5–10 years (2–4). More recently, the development of referral strategies for early inflammatory back pain (IBP) (5–7) and the use of magnetic resonance imaging (MRI) to visualize active sacroiliitis have probably decreased this diagnostic delay. However, detecting the earliest phases of the disease remains challenging, which has 3 potentially important implications. First, the absence of an early diagnosis delays adequate treatment of signs and symptoms of inflammation for several months to years. Second, uncontrolled early disease may initiate osteoproliferation, a process seemingly resistant to treatment in the later phases (8–10). Third, when the earliest phase of the disease is ignored, a comprehensive chronological and hierarchical mapping of all cellular and molecular mechanisms that drive SpA is elusive (11,12). Similar to rheumatoid arthritis, SpA might have a subclinical phase of disease preceding the clinical established phase, in which abnormalities are present but clinical symptoms are lacking. A systematic screening and meticulous follow-up of those who are at high risk of developing SpA may help to address such challenges. Models explaining the genetic susceptibility to ankylosing spondylitis (AS), the prototypical axial form of SpA, suggest an 8% risk of AS in first-degree relatives of AS patients (13). The comparison of familial and sporadic cases of AS suggests a higher familial aggregation of AS in patients who are positive for HLA–B27 (14). Accordingly, several studies have suggested a 10–12% risk of AS (as defined by the presence of radiographic sacroiliitis) in first-degree relatives of AS patients, with a 2-fold higher risk in HLA–B27–positive individuals (15–18). Other SpA subtypes were also frequently observed in first-degree relatives of probands with AS or SpA (18,19). Because all these cross-sectional studies consistently show that first-degree relatives of HLA–B27– positive AS patients have a strongly increased risk of developing SpA, prospective analysis of such first- degree relatives at risk opens the way to systematic and detailed characterization of the earliest phases of SpA. In order to better detect, understand, and eventually treat the earliest phases of disease, the purpose of the present inception cohort study was to prospectively study the appearance and development of clinical, biologic, and imaging (radiographic and MRI) features of SpA in seemingly healthy first-degree relatives of AS patients. Herein we report the baseline analysis of clinical and imaging features in 51 first-degree relatives included in the study.
PATIENTS AND METHODS
Study design
Pre-spondyloarthritis (Pre-SpA) is an ongoing, prospective 5-year inception cohort study. First-degree relatives of HLA–B27–positive AS patients were included;
THE PRE-SPA COHORT
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