Original contribution Merkel cell polyomavirus DNA sequences in peripheral blood and tissues from patients with Langerhans cell histiocytosis ☆,☆☆ Ichiro Murakami MD, PhD a, ⁎ , Michiko Matsushita MT, MA b , Takeshi Iwasaki MD a , Satoshi Kuwamoto MD, PhD a , Masako Kato MD, PhD a , Yasushi Horie MD, PhD c , Kazuhiko Hayashi MD, PhD a , Toshihiko Imamura MD, PhD d , Akira Morimoto MD, PhD e , Shinsaku Imashuku MD, PhD f , Jean Gogusev MD, PhD g , Francis Jaubert MD, PhD h , Katsuyoshi Takata MD, PhD i , Takashi Oka PhD, DMSc i , Tadashi Yoshino MD, PhD i a Division of Molecular Pathology, Faculty of Medicine, Tottori University, Yonago 683–8503, Japan b Department of Pathobiological Science and Technology, School of Health Science, Faculty of Medicine, Tottori University, Yonago 683–8503, Japan c Department of Pathology, Tottori University Hospital, Yonago 683–8503, Japan d Department of Pediatrics, Kyoto Prefectural University of Medicine, Kyoto 602–8566, Japan e Department of Pediatrics, Jichi Medical University School of Medicine, Shimotsuke 329–0498, Japan f Division of Pediatrics and Hematology, Takasago-seibu Hospital, Takasago 676–0812, Japan g Inserm U507 and U1016, Institut Cochin, 75014 Paris, France h University of Paris Descartes (Paris V), 75006 Paris, France i Department of Pathology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700–8530, Japan Received 23 April 2013; revised 29 May 2013; accepted 31 May 2013 Keywords: Merkel cell polyomavirus; Langerhans cell histiocytosis; Langerhans cells; Dermatopathic lymphadenopathy; Multiplex quantitative real-time PCR Summary Langerhans cell histiocytosis (LCH) is a group of granulomatous disorders in which abnormal Langerhans cells proliferate as either a localized lesion in a single bone or disseminated disease involving two or more organs or systems. Because the different LCH forms exhibit significantly elevated levels of inflammatory molecules, including pro-inflammatory cytokines and tissue-degrading enzymes, we investigated for a possible viral trigger in LCH pathogenesis. We looked for Merkel cell polyomavirus (MCPyV) in peripheral blood cells and tissues using quantitative real-time PCR and immunohistochemistry staining with anti-MCPyV large T-antigen antibody. Our findings revealed elevated amounts of MCPyV DNA in the peripheral blood cells of 2 of 3 patients affected by LCH with high-risk organ involvement (RO+) and absence of MCPyV DNA in the blood cells in all 12 LCH-RO- patients (P=.029). With lower viral loads (0.002-0.033 copies/cell), an elevated number of MCPyV DNA sequences was detected in 12 LCH tissues in comparison with control tissues obtained from ☆ Competing interests: The authors declare no competing financial interests. ☆☆ Funding/Support: This work was partly supported by a Grant-in-Aid for Scientific Research (C) 23590426 from the Japanese Ministry of Education, Science, Sports and Culture and by 2010 and 2011 research grants from the Japan LCH Study Group. ⁎ Corresponding author. E-mail address: ichiro.murakami.09@gmail.com (I. Murakami). www.elsevier.com/locate/humpath 0046-8177/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.humpath.2013.05.028 Human Pathology (2014) 45, 119–126