血吞噬细胞淋巴组织细胞增生症（HLH）是一种高致死率的疾病，其特征为发热、细胞减少、脾肿大和血吞噬现象。虽然感染性疾病、恶性肿瘤和自身免疫性疾病常常是HLH的诱因，但与疫苗相关的HLH的报告很少。在本报告中，我们描述了一例12岁女性患者，在接种二价mRNA型严重急性呼吸综合症冠状病毒2（SARS-CoV-2）疫苗和四价灭活型流感疫苗后出现HLH的病例。患者在接种后的第二天因发热而来我院就诊。考虑到脾肿大、细胞减少、骨髓中的血吞噬现象和高铁蛋白水平，12天后诊断为HLH。各种检测排除了任何感染性疾病、恶性肿瘤或自身免疫性疾病。患者仅使用2mg/kg/天的口服泼尼松治疗，13天后发热好转，血液检查结果迅速改善。尽管SARS-CoV-2疫苗接种后或与流感疫苗同时接种后出现的HLH仍然很少见，但我们强调当接种后出现持续发热时，早期诊断HLH的重要性。版权所有©2023日本化疗学会、日本传染病学会和日本感染预防控制学会。由Elsevier Ltd.出版。保留所有权利。

Hemophagocytic lymphohistiocytosis (HLH) is a highly lethal disease characterized by fever, cytopenia, splenomegaly, and hemophagocytosis. Whereas infectious diseases, malignant tumors, and autoimmune diseases are often triggers for HLH, reports of HLH associated with vaccination are limited. In this report, we describe a case of HLH in a 12-year-old female patient after simultaneous administration of the bivalent messenger RNA severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine and quadrivalent inactivated influenza vaccine. The patient presented to our hospital with fever on the day after vaccination. Considering the splenomegaly, cytopenia, hemophagocytosis in the bone marrow, and high ferritin level, HLH was diagnosed 12 days after vaccination. Various tests ruled out any infectious disease, malignant tumor, or autoimmune disease. The patient was treated only with 2 mg/kg/day of oral prednisolone, fever improved 13 days after vaccination, and blood test findings rapidly improved. Although HLH after SARS-CoV-2 vaccination or concomitant administration with influenza vaccination is still rare, we emphasize the importance of early HLH diagnosis when persistent fever is observed following vaccination.Copyright © 2023 Japanese Society of Chemotherapy, Japanese Association for Infectious Diseases, and Japanese Society for Infection Prevention and Control. Published by Elsevier Ltd. All rights reserved.