Overlap of systemic lupus erythematosus and myositis is rare in anti-Ku antibody-positive patients

Abstract

Contributors MO conceived the hypothesis, analysed data and drafted the manuscript; YM conceived the hypothesis, analysed data, critically revised the manuscript and gave final approval; MA analysed data, critically revised the manuscript and gave final approval.

Immune-mediated necrotizing myopathies and interstitial lung disease are predominant characteristics in anti-Ku positive patients with idiopathic inflammatory myopathies

“…Skin involvement was less common among patients with isolated anti-Ku than that among patients showing coexistence of anti-Ku and MSA (18.2% vs 70%, p=0.03). ILD presented in 76.2% of anti-Ku-positive IIM patients, consistent with the high frequency of ILD reported in previous studies 1 2. Although there was no significant difference in the incidence of ILD between patients with isolated anti-Ku and anti-Ku coexistence with MSA, patients with isolated anti-Ku had a lower mean percentage of predicted value for FVC and DLco than those with coexistence of anti-Ku and MSA(74.05%±12.84% vs 93.21±18.54% and 59.61±15.41% vs 76.03±14.15%, p=0.035 and 0.049, respectively).…”

Anti-Ku antibodies: important points to consider

“…With interest, we read the recent article by Ogawa-Momohara et al 1 which reports the clinical phenotype of patients with anti-Ku autoantibodies and conclude that systemic lupus erythematosus (SLE) and myositis overlap is rare in patients with this antibody reactivity. Ku is a well-known protein heterodimer comprised of 70 and 80 kDa subunits and is best-known for its central role in binding to DNA and the double-strand break DNA repair pathway in mammals 2…”

“…In addition, if patients are preselected based on HEp-2 indirect immunofluorescence (IIF) patterns, a potential exclusion bias is introduced (figure 2). In the correspondence by Ogawa-Momohara et al ,1 samples were preselected based on the HEp-2 IIF pattern that has been historically associated with anti-Ku antibodies (ICAP nomenclature AC-04; www.anapatterns.org). 8 This approach introduces a potential bias because patients with SLE frequently express many autoantibodies9 and sera accompanied by mixed HEp-2 IIF patterns are very common and presumably were excluded in this study.…”

“…The observation that a significant portion of anti-Ku-positive patients also exhibit anti-dsDNA antibodies is complicated by the known variability between anti-dsDNA assays 12. In the correspondence by Ogawa-Momohara et al ,1 no information is provided on the methods used for the detection of anti-dsDNA and anti-ssDNA antibodies. Therefore, the interpretation of the results in this study is difficult.…”

Response to: ‘Anti-Ku antibodies: important points to consider’ by Mahler et al

“…We thank the authors1 for their interest in our paper2 and are grateful for the opportunity to respond to the points raised. We agree with the opinion of Mahler et al that ‘SLE frequently express many autoantibodies and sera accompanied by mixed HEp-2 IIF pattern were very common’.…”