As many as one-third of healthy first-degree relatives of individuals with ankylosing spondylitis may meet the criteria for spondyloarthritis, according to results from a prospective cohort study.
Dr. Maureen C. Turina of the Amsterdam Rheumatology and Immunology Center at the University of Amsterdam and her coauthors enrolled 51 first-degree relatives of individuals with HLA-B27–positive ankylosing spondylitis in the study to see whether any of these otherwise healthy individuals showed early signs of the disease. They found that 17 (33%) of these first-degree relatives fulfilled any of the spondyloarthritis (SpA) classification criteria at baseline – a higher rate than reported in previous studies – and 7 (14%) met both the Assessment of Spondyloarthritis International Society (ASAS) criteria and European Spondyloarthropathy Study Group (ESSG) criteria.
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The authors suggested that the higher rate, compared with previous studies, could be due to channeling bias, as individuals with clinical symptoms may have been more willing to participate in the study.
However, 4 of the 38 individuals who did not fulfill either of these criteria for SpA still showed imaging abnormalities – including syndesmophytes on the cervical spine and bone marrow edema in the sacroiliac joint.
The authors suggested these imaging abnormalities may represent a subclinical phase of SpA (Arthritis Rheumatol. 2016 May 23. doi: 10.1002/art.39766).
The participants who met the ASAS and/or ESSG classification criteria for SpA had more axial, entheseal, and joint pain, compared with those who did not meet the criteria. All of these patients also reported back pain, compared with 35% of those who did not fulfill the criteria.
However, the individuals meeting the SpA criteria had low overall disease scores, and did not show any increase in inflammatory serum markers.
“Importantly, some key features of SpA including the presence of peripheral disease or extra-articular manifestations and increased inflammatory parameters were only rarely observed in FDRs [first-degree relatives] and were also not different in those fulfilling the ASAS axSpA and/or ESSG classification criteria versus those who did not,” the authors reported.
“Future follow-up will learn if and which of these FDRs will evolve into the clinically established phase of SpA.”
When specifically asked, more than half (57%) of the first-degree relatives said they had back pain, and 40% said they had experienced or were experiencing arthralgia.
“The fact that these FDRs were not investigated for or diagnosed with axial SpA before inclusion in the study may be related either to the fact that the back pain symptoms were relatively mild or to ignorance of general physicians for these alarm symptoms,” the authors wrote.
One person said they had past or present peripheral arthritis but none reported enthesitis or dactylitis.
While none of the subjects had arthritis, 16% reported at least one tender joint, and 22% had a modified Schober score of less than 4.5 cm, with 4% showing a chest expansion of less than 3.6 cm.
Researchers also examined whether HLA-B27 status had any impact on the first-degree relatives, as previous studies had suggested that SpA is more likely to present in HLA-B27–positive first-degree relatives.
However they found no differences between the HLA-B27–positive and HLA-B27–negative groups in terms of demographics, symptom history, disease activity, clinical examination, or laboratory or imaging data; a finding the authors described as “intriguing.”
“However, if confirmed in a larger sample set, further follow-up of these FDRs will allow us to determine if FDRs showing signs and symptoms of SpA will evolve to more active and severe disease, independently of HLA-B27 status or, alternatively, if the presence of HLA-B27 may promote exacerbation and persistence of subclinical pathology.”
The study was supported by the Dutch Arthritis Foundation. No conflicts of interest were declared.