As first-degree relatives (FDRs) of HLA-B27-positive axial spondyloarthritis (axSpA) patients have an increased risk of developing axSpA, the objectives were 1) to evaluate presence of highly specific imaging features as well as clinical signs of SpA at baseline and after one year of follow-up, and 2) describe the evolution towards clinical disease within one year of follow-up in a cohort of seemingly healthy FDRs of HLA-B27 positive axSpA patients.
The Pre-SpA cohort is a 5-year prospective inception cohort of seemingly healthy FDRs of HLA-B27 positive axSpA patients. Clinical and imaging features were collected and recorded.
At baseline 19% of the FDRs reported inflammatory back pain. Thirty-two percent reported current arthralgia, 3% arthritis (ever), 5% enthesitis (ever) and 1% dactylitis (ever). Three percent had an extra-articular manifestation. CRP was elevated in 16%, ESR in 7%. On MRI-SIJ, 10% had a SPARCC score ≥2, 4% ≥5, and 4% deep lesions. One percent fulfilled the mNY criteria for radiographic sacroiliitis. Clinical, MRI and acute phase findings were equally distributed between HLA-B27 positive and negative FDRs. After 1 year of follow-up, clinical parameters did not change on the group level but 6% of the FDRs were clinically diagnosed with axSpA, of whom 86% were HLA-B27 positive.
Features associated with spondyloarthritis or imaging abnormalities were found in up to 32% of seemingly healthy FDRs, with an equal distribution between HLA-B27 positive and negative FDRs. Progression to clinical axSpA within 1 year of follow-up was mainly observed in HLA-B27 positive FDRs.