Polymyositis/dermatomyositis and nasopharyngeal carcinoma: The Epstein–Barr virus connection?
Section snippets
Background
Polymyositis (PM)/dermatomyositis (DM) are inflammatory muscular diseases,1, 2 and are the outcome of autoimmunity that results in injuries to muscle fibers.3, 4, 5 The best defined myositis-specific autoantigens are transfer RNA-synthase, and the prevalence of anti-synthetase antibodies (ASA) is up to 20–37% in PM/DM patients.6, 7 However, the etiopathogenesis of PM/DM remains unclear.
Viral infection might induce autoimmunity in susceptible individuals.8, 9 The reported seasonal occurrence of
Objectives
This study is the first attempt to investigate the associations of EBV infection with clinical manifestations and the occurrence of NPC in PM/DM patients. We re-examine the association between EBV infection and PM/DM using serologic assays for IgA anti-EBNA-1 antibody responses to a fragment of EBNA-1 lacking cross-reactive epitopes, and using real-time quantitative polymerase chain reaction (RQ-PCR) to determine EBV DNA loads. To test whether the emergence of NPC in myositis patients was the
Patients and matched controls
Ninety-eight adult patients fulfilling the Bohan and Peter criteria of PM/DM30, 31 were enrolled. After investigation, all patients were treated with corticosteroids and immunosuppressive agents. Ninety-four consecutive patients fulfilling the 1997 revised criteria for SLE32 and continuously receiving immunosuppressant were enrolled as disease control. Three hundred and seventy healthy volunteers who had no rheumatic disease or malignancy served as healthy controls (HC) by matching for sex and
Clinical characteristics and laboratory findings
Thirteen (13.3%) PM/DM patients had a detectable NPC, while none of SLE patients developed NPC during the 10-year follow-up period. As illustrated in Table 1, significantly lower proportion of females and interstitial lung disease was observed in PM/DM patients with NPC compared with those without malignancy. Interestingly, a lack of detectable ASA was observed in any myositis patient with NPC. There were no significant differences in the mean doses of daily corticosteroids or the proportion of
Discussion
The etiology of PM/DM remains unclear, but various causative factors including autoantibodies, genetic susceptibility, and viral infection have been postulated.3, 35, 36, 37, 4, 5, 6, 7, 8 The role of EBV infection in PM/DM was suspected.37, 8 We showed a significantly higher positive rate for IgA anti-EBV EBNA-1 and EBV DNA genome in sera of PM/DM patients compared with HC, which supports an association of EBV with myositis. Similarly, significantly higher positive rates for IgA anti-EBV
Conflict of interest
None.
Acknowledgements
Funding: This study was supported by Taichung Veterans General Hospital and National Taichung Nursing College, Taiwan (Grant TCVGH-NTCNC-978502).
Competing interests: None declared.
Ethical approval: The study protocol was approved by the Ethics Committee of Taichung Veterans General Hospital.
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