Undifferentiated spondyloarthritis in a heterogeneous Brazilian population: an eight-year follow-up study

The aim of the present study was to describe the outcomes of Brazilian patients with undifferentiated spondyloarthritis during an eight-year follow-up period. Patients fulfilling the European Spondyloarthritis (SpA) Study Group Classification Criteria were enrolled. Forty patients were seen at baseline, and 36 participated in the follow-up study. Twenty-three (58 %) were female, and there were 24 (60 %) African Brazilians enrolled. HLA-B27 was positive in 18 (45 %) patients. At disease onset, the first presenting symptoms were pure peripheral manifestations in 26 (72.2 %) patients. After the study period, mixed disease (axial + peripheral) predominated occurring in 25 (69.4 %) patients. The Assessment of SpA International society (ASAS) classification criteria for axial SpA were fulfilled by 77 % of patients, and the ASAS criteria for peripheral SpA were fulfilled by 59 % of patients. After 2.5 years, 6 (16.7 %) of the 36 patients fulfilled the modified New York Criteria for ankylosing spondylitis and 1 (2.7 %) progressed to psoriatic arthritis. A total of 10 (27.8 %) patients progressed to definite SpA during the eight-year study period. Buttock pain (p = 0.006, OR 10.55; 95 % CI 2.00–65.90) and low-grade radiographic sacroiliitis (p = 0.025, OR = 11.50; 95 % CI 1.33–83.39) at baseline were associated with definite SpA. Thus, in this Brazilian cohort, which had a predominance of female African-Brazilian patients, prevalent peripheral onset symptoms were followed by a high frequency of axial manifestations during the follow-up period. Evidence of clinical or radiological sacroiliitis was associated with progression to definite SpA.