All authors read and approved the final manuscript. == Ethics approval and consent to participate == Not applicable. == Consent for publication == Written informed consent was obtained from the surviving patient and the families of the deceased patient for publication of this case report and any accompanying images. (APTT), elevated hepatic enzyme. The two patients recovered with treatment of doxycycline, human immunoglobulins, plasma transfusion, and other supporting treatments. But case 1 occurred lymphoma 8 months later and died. == Conclusion == SFTS might be one of differential diagnosis of MM in certain endemic area. We also conclude that SFTSV is a pantropic virus that could injure most tissues and cells of the human body. Keywords:Severe fever with thrombocytopenia syndrome, SFTS, Reactive plasmacytosis, Multiple myeloma == Background == Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease with a constellation of clinical signs and symptoms, including fever, gastrointestinal symptoms, hemorrhagic tendency, thrombocytopenia, leukocytopenia, elevated serum enzyme levels, and regional lymphadenopathy [1]. The etiological AdipoRon pathogen, severe fever with thrombocytopenia syndrome virus (SFTSV), was first identified by Chinese Center for Disease Control and Prevention (China CDC) in 2010 2010 [2]. Ticks are considered potential transmission vectors of SFTS, however, there have been several reports of human-to-human transmission [35]. Although SFTS has multiple manifestations, reactive plasmacytosis is an extremely rare condition in association with SFTS. Here we describe two patients with SFTS who presented with reactive plasmacytosis, mimicking multiple myeloma (MM). In addition, we discuss the clinical and laboratory characteristics of the SFTS cases. Also, the clinical data of 4 Asian patients with SFTS associated reactive plasmacytosis is summarized. == Cases presentation == == Case 1 == A 63 year-old male farmer with a history of a tick bite presented with a sudden onset of fever on May 28, 2014, with a temperature of 38.6 C, AdipoRon accompanied by rash, nausea, anorexia, fatigue, enlarged AdipoRon lymph node, and general body aches. He presented to the emergency department of The First Affiliated Hospital of China Medical University (CMU) on June 4. Routine blood tests showed leukocytosis with peripheral blood plasmacytosis (white blood cell [WBC] count, 24.46 109/L; proplasmacytes, 5%; mature plasma cells, 18%) and thrombocytopenia (platelets[PLT], 75 109/L). Cytological examination of the bone marrow demonstrated plasmacytosis. With a AdipoRon preliminary diagnosis of MM, he was admitted to the Department of Hematology of CMU on June 6. Physical examination revealed palpable swollen lymph nodes in the submandibular and bilateral axillary regions, accompanied with dispersed red papules on chest and abdomen. Laboratory tests upon admission showed thrombocytopenia, increased alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) levels, prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT). Immunofixation by electrophoresis revealed a polyclonal pattern with increased amounts of immunoglobulin (IgA, IgG, and IgM) and immunoglobulin light chains. Proteinuria was observed but Bence Jones proteinuria was negative. Because of abnormal bone marrow cytology, X-ray AdipoRon of skull, thoracic and Rabbit Polyclonal to Keratin 15 lumbar vertebrae, and pelvis was performed, with normal findings. ELISA and RT-PCR were performed to detect SFTSV-specific IgM/IgG and SFTSV RNA as previously described [2,6]. And the IgM antibody and RNA to SFTSV were positive. Bone marrow cytology showed plasmacytosis, with plasma cells accounting for 29.2% of all nucleated cells, including proplasmacytes (6.8%) and mature plasma cells (22.4%) (Fig.1). However, flow cytometric immunophenotyping (FCI) of bone marrow revealed that the increased plasma cells were not monoclonal (Fig.2). The patient was administered doxycycline, human immunoglobulins, plasma transfusion and other supporting treatments, and was improved. Finally, a diagnosis of reactive plasmacytosis associated with SFTS was reached. The clinical and laboratory findings are summarized in Table1. == Fig. 1. == Representative images of bone marrow cytology(Wright and Giemsa stain) showing plasmacytosis.aFor case 1, (bandc) for case 2 at different time points == Fig. 2. == Representative scatter plots of bone marrow flow cytometric immunophenotyping. (a-c) For case 1, the incresed plasma cells were polyclonal (CD19 + CD38 + CD138 + cKappa+cLambda+) (d-f) for case 2, the incresed plasma cells were abnormal monoclonal (CD19 + CD38 + CD138 +.