The B7 cross reactive group and spondyloarthropathies : an epidemiological approach

Objective. To study the association between the B7 cross reactive group (B7, B40) and spondyloarthropathy (SpA), taking into account patients with atypical features. Methods. We studied the main clinical and paraclinical features of 51 patients with rheumatoid arthritis, 55 with SpA, 120 with mechanical diseases, and 160 with inflammatory rheumatism not fulfilling the diagnostic criteria currently used. This descriptive analysis was performed using multiple correspondence factorial analysis to identify subgroups among unclassified patients and select SpA variants. We compared HLA frequencies among these groups versus a control group. Results. We identified a subgroup close to the axial SpA and related to B7 (OR : 5.91, p = 0.0008), whereas B40 is related to patients close to the peripheral SpA. Conclusion. B7 is related to axial SpA variants manifested by inflammatory low back pain according to Calin's criteria, with either extraarticular signs or sacroiliitis. Followup of such patients is equired to determine whether their disease is a new entity or can be considered SpA.