Uncorrected Proof Arch Pediatr Infect Dis. In Press(In Press):e83564. Published online 2020 February 17. doi: 10.5812/pedinfect.83564. Case Report Secondary Hemophagocytic Lymphohistiocytosis in a Child with Brucellosis Abdollah Karimi 1 , Abas Solgi 1 , Zahra Pourmoghaddas 1, * , Maryam Kazemiaghdam 2 and Reyhan Zojaji 1 1 Pediatric Infection Research Center, Research Institute for children Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Pediatric Pathology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran * Corresponding author: Pediatric Infection Research Center, Research Institute for children Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Email: zahrapormoghadas@yahoo.com Received 2018 August 24; Revised 2020 January 24; Accepted 2020 January 26. Abstract Brucellosis, with multi-organ involvement, is recognized as a zoonotic infection in Iran. This infection has multiple signs and symp- toms. On the other hand, hemophagocytic lymphohistiocytosis (HLH) is described as an uncommon disorder. The secondary type of this disease may be associated with infection. However, the association between HLH and brucellosis has been rarely reported, especially in pediatric populations. Herein, we present a pediatric case of secondary HLH associated with brucellosis. Based on our findings, HLH should be considered in patients diagnosed with brucellosis with profound cytopenia and increased spleen size despite treatment. Keywords: Brucella, Hemophagocytic Lymphohistiocytosis, Child 1. Introduction Brucellosis is the most prevalent zoonotic infection in Iran, especially in west and northwest regions of the country (1). The high prevalence of brucellosis has made this infection a public health concern (2). In children, it is associated with fever, sweating, hepatosplenomegaly, and arthritis of large joints. Anemia, leukopenia or leukocytosis, thrombocytopenia, and increased concen- tration of C-reactive protein (CRP), erythrocyte sedimen- tation rate (ESR), and liver function tests are the most common laboratory findings on brucellosis assessment (3). Hemophagocytic lymphohistiocytosis (HLH) repre- sents non-malignant generalized proliferation of histio- cytes, with marked hemophagocytosis in the liver, bone marrow, spleen, and central nervous system (4-6). As mentioned earlier, cytopenia, high fever, and hep- atosplenomegaly are common presentations of brucel- losis, while pancytopenia is not common in this infection (7, 8). Herein, we present a case of secondary HLH associ- ated with brucellosis. 2. Case Presentation A three-year-old boy was admitted to our hospital with one month of fever, cough, and fatigue, without weight loss or arthralgia. He was hospitalized for pervious 2 weeks in another hospital for evaluation of FUO and cytopenia. The results of pervious evaluation showed pancytopenia, fasting triglyceride (TG) level: 338 mg/dL, ferritin level of > 800 ng/mL, and bone marrow aspiration (BMA) reported normal. In his past medical history, consumption of ice cream, as an unpasteurized milk product, was reported. Based on examination upon admission, he was conscious, well- oriented, pale, and febrile (about 39°C), with a pulse rate of 120/min, blood pressure of 96/65 mmHg, respiratory rate of 26/min, and capillary refill time of < 3 seconds. Spleen and liver palpated 4 cm and 11 cm below the costal mar- gin respectively. We repeated the evaluations by ordering complete blood cell count (CBC), Blood culture, aspartate transaminase (AST) and alanine transaminase (ALT) levels, peripheral blood smear for Malaria, Tuberculin skin test (TST), Wright and Coombs Wright, viral capsid antibody (VCA), and anti cytomegalovirus antibodies, ESR and CRP. According to our analyses, the level of hemoglobin was 8.1 mg/mL the total leukocyte count (WBC) was 4100/mm 3 (neutrophil = 27%; lymphocyte = 70%), and the platelet count was 38000/mm 3 . ESR and CRP were 37 mm/hour and 53 mg/dL, respectively. The biochemical analysis showed (AST) (ALT) levels of 330 U/L and 74 U/L, respec- Copyright © 2020, Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.