Background It has been recognized for a long time that about 60% of all spondyloarthritis (SpA) patients show microscopic inflammatory gut lesions, a fraction of which evolves into Crohn’s disease(1). Recently, this high prevalence of microscopic gut inflammation was confirmed in a patient cohort fulfilling the Assessment of SpondyloArthritis International Society (ASAS) criteria for axial and peripheral SpA (Gent Inflammatory Arthritis and spoNdylitis cohort - GIANT), and several risk factors for microscopic gut inflammation were identified(2). Magnetic Resonance Imaging (MRI) enables us to identify early in the disease course patients with non-radiographic axial SpA (nr-axSpA) by assessing bone marrow edema (BME) of the sacroiliac joints (SIJ). However, the correlation between the extent of BME and disease activity remains unclear.

Objectives This study was designed to assess the link between BME of the SIJ and gut inflammation. Furthermore, we have evaluated the correlation between BME and established disease activity parameters.

Methods The GIANT cohort is a prospective observational cohort in which patients diagnosed with axial and peripheral SpA according to the ASAS criteria are prospectively followed; at present 150 SpA patients have been included. Ileocolonoscopy was performed in 54 patients (28 men and 26 women), never being treated with TNF blockers. Two patients had a history of inflammatory bowel disease. Mean age was 33.9 years. Eighty percent of the patients were HLA-B27 positive. Bone marrow edema was assessed by the Spondyloarthritis research consortium of Canada (SPARCC) score(3) and linked to the presence of gut inflammation. Patients with total ankylosis of the SIJ were excluded from this analysis as they showed no BME.

Results A normal gut histology was found in 55.6% of all patients, 11.1% patients showed acute lesions and in 33.3% chronic lesions were found. SPARCC scores were significantly higher (median, [interquartile range]) in the group of patients showing gut inflammation (16.5 [23.6]) compared to those with normal histology (9.0 [15.4], p= 0.042). The degree of BME was most pronounced in patients with chronic lesions. SPARCC scores correlated moderately with C-reactive protein (CRP)(r=0.418, p=0.003), whereas no correlation with BASDAI or ASDAS was seen.

Conclusions Higher degrees of BME were observed in patients showing gut inflammation. There was a moderate correlation between the degree of BME and CRP. These data solidify a link between mucosal inflammation and the degree of sacroiliac joint inflammation in axial spondyloarthritis.

References

1. Mielants H, Veys EM, Cuvelier C, et al. The evolution of spondylarthropathies in relation to gut histology. II. Histological aspects. J. Rheumatol. 1995;22(12):2273-8.

2. Van Praet L, Van den Bosch FE, Jacques P, et al. Microscopic gut inflammation in axial spondyloarthritis: a multiparametric predictive model. Ann Rheum Dis 2012. Nov 8. [Epub ahead of print]

3. Maksymowych WP, Inman RD, Salonen D, et al. Spondyloarthritis research consortium of Canada magnetic resonance Imaging index for assessment of sacroiliac joint inflammation in ankylosing spondylitis. Arthrit Rheum-Arthr 2005;53:703-709.

Disclosure of Interest None Declared