Introduction: Antinuclear antibody (ANA) tests are widely used for the diagnosis of autoimmune diseases, but ANAs are also commonly found in patients with various infections. This retrospective study aimed to investigate the relationship between infections and ANA status. Methods: Patients that visited the Department of Infectious Diseases at Inha University Hospital between January 2007 and July 2018 were investigated. We analysed their ANA test results and reviewed rheumatic and infectious diagnoses of patients with positive ANA findings. Results: Of the 9,320 patients during the study period, 1,111 underwent ANA testing and 110 tested positive. Seven of the 110 patients were previously diagnosed with ANA-positive disease, and 21 were diagnosed with autoimmune disease during the present study. Of the remaining 82 patients, 43 were confirmed with infectious disease. The most common pathogen was Mycobacterium tuberculosis (n = 10), followed by Treponema pallidum (n = 5), Orientia tsutsugamushi (n = 5), Escherichia coli (n = 5), Bartonella henselae (n = 3), and human immunodeficiency virus (n = 3). Of the 39 patients without a confirmed pathogen, 7 were seropositive for O. tsutsugamushi, B. henselae, or Rickettsia spp. Patients were observed at an average of 24 weeks in our hospital. One patient developed systemic lupus erythematosus after being diagnosed with Epstein–Barr virus-induced infectious mononucleosis, and another patient developed adult-onset Still’s disease after being diagnosed with scrub typhus. Conclusion: This study showed that various relationships exist between infections and rheumatic diseases. In particular, several patients with a positive ANA test result were found to have intracellular infections such as mycobacterial infections, syphilis, or scrub typhus.

Im JH, et al. J Korean Med Sci. 2020 May;35(27):e239. https://doi.org/10.3346/jkms.2020.35.e239

Im JH, et al. Yonsei Med J. 2021 Dec;62(12):1162-1168. https://doi.org/10.3349/ymj.2021.62.12.1162

Kang H, et al. J Korean Med Sci. 2023 Oct;38:e346. https://doi.org/10.3346/jkms.2023.38.e346

Im JH, et al. J Korean Med Sci. 2021 Jan;36(5):e42. https://doi.org/10.3346/jkms.2021.36.e42

Tsutsugamushi disease, or scrub typhus, is an acute febrile illness caused by Orientia tsutsugamushi, which is followed by chronic latent infection. People who reside in areas endemic of tsutsugamushi disease may be frequently reinfected with this organism. Volunteers who are experimentally reinfected with O. tsutsugamushi manifest various systemic and local reactions, including the presence of small-sized eschar. The present study recorded the morphology and size of eschars in patients with tsutsugamushi disease on Jeju Island, Korea. From March 2018 to February 2019, 23 patients manifesting clinical characteristics and epidemiologic features of tsutsugamushi disease on Jeju Island were investigated. For comparison of eschar sizes between the two regions, 12 patients with tsutsugamushi disease in Incheon were similarly examined. Three patients, two on the first day and one on the fourth day of fever, presented with papules of 2 - 5 mm in diameter. Another three patients, one on the second day and two on the fourth day, presented with ruptured vesicles of 5 - 8 mm in diameter. Thirteen patients presented with eschars covered with dark scabs, with a median diameter of 5 (95% confidence interval [CI], 5 - 7.5) × 4 (95% CI, 3 - 5) mm. The medians of the eschar sizes did not differ between the two cities (P = 0.46 by Mann-Whitney U test), but eschars ≥10 mm in diameter were more frequent in Incheon than in Seogwipo-si (4 of 12 vs. 0 of 13 patients, P = 0.04 by Fisher's exact test). One patient presented with multiple eschars, and no eschar was detected in the remaining three patients. Among 11 Jeju Island patients with positive IgG and IgM antibodies, seven patients revealed higher IgG than IgM antibody titers during the acute phase of the illness, i.e., the IgG antibody response, two patients had equal IgG and IgM titers, and two patients presented the IgM antibody response. Life-threatening complications and death were not observed in this study. The patients in Seogwipo-si had small-sized eschars and occasionally exhibited non-necrotic lesions. Many patients had serologically reinfected tsutsugamushi disease. Further studies are needed to investigate the association between these findings.