Objectives: To determine the prevalence of anti-Ku antibodies in 625 patients with systemic sclerosis (SSc) from six European rheumatological centres and to evaluate their clinical and serological characteristics.
Methods: Sera of 625 consecutive patients with either limited cutaneous or diffuse cutaneous SSc were tested for antibodies to Ku antigen together with other extractable nuclear antigens by counterimmunoelectrophoresis. A case–control design with calculation of bootstrap 95% confidence intervals derived from anti-Ku negative control patients was used to evaluate clinical associations of anti-Ku antibodies. Sera from anti-Ku positive patients with SSc and a control group were additionally tested by immunofluorescence on Hep-2 cell substrates and line immunoassay.
Results: Anti-Ku antibodies were found in the sera of 14/625 (2.2%) patients with SSc. Of 14 anti-Ku positive patients with SSc, 10 had no other anti-extractable nuclear antigen (ENA) antibodies detected by counterimmunoelectrophoresis. Using a case–control study design, anti-Ku antibodies were significantly associated with musculoskeletal manifestations such as clinical markers of myositis, arthritis and joint contractures. In addition, a significant negative correlation of anti-Ku antibodies was found with vascular manifestation such as fingertip ulcers and teleangiectasias. There was a striking absence of anti-centromere antibodies as well as anti- polymyositis (PM)/scleroderma (Scl) antibodies in patients that were anti-Ku positive. As expected, anti-Scl70 and punctate nucleolar immunofluorescence patterns were present only in single cases.
Conclusion: This is the largest cohort to date focusing on the prevalence of anti-Ku antibodies in patients with SSc. The case–control approach was able to demonstrate a clinically distinct subset of anti-Ku positive patients with SSc with only relative clinical differences in skeletal features. However, the notable exceptions were signs of myositis. This shows the importance of anti-Ku antibody detection for the prediction of this specific clinical subset.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.
Funding: This study was partially supported by Ministry of Higher Education, Science and Technology of Slovenia (grant no.: P3-0314).
Competing interests: None declared.
Ethics approval: This study was approved by The National Medical Ethics Committee of the Republic of Slovenia.