Hemophagocytic lymphohistiocytosis (HLH) is a syndrome describing patients with severe systemic hyperinflammation. Characteristic features include unremitting fever, cytopenias, hepatosplenomegaly, and elevation of typical HLH biomarkers. Patients can develop hepatitis, coagulopathy, liver failure, central nervous system involvement, multi-organ failure, and other manifestations. The syndrome has a high mortality rate. More and more, it is recognized that while HLH can be appropriately used as a broad summary diagnosis, many pediatric patients actually suffer from an expanding spectrum of genetic diseases that can be complicated by the syndrome of HLH. Classic genetic diseases in which HLH is a typical and common manifestation include pathogenic changes in the Familial HLH genes (PRF1, UNC13D, STXBP2, STX11), several granule/pigment abnormality genes (RAB27A, LYST, AP3B1), the X-linked lymphoproliferative disease genes (SH2D1A, XIAP), and others such as NLRC4, CDC42, and the EBV-susceptibility diseases. There are many other genetic diseases in which HLH is an infrequent complication of the disorder as opposed to a prominent manifestation of the disease caused directly by the genetic defect, including other primary immune deficiencies and inborn errors of metabolism. HLH can also occur in patients with underlying rheumatologic or autoinflammatory disorders, and is usually designated macrophage activation syndrome in those settings. Additionally, HLH can develop in patients during infections or malignancies without a known (or as yet identified) genetic predisposition. This article will attempt to summarize current concepts in the pediatric HLH field as well as offer a practical diagnostic and treatment overview.

中文翻译：

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小儿噬血细胞淋巴组织细胞增生症 (HLH)

噬血细胞性淋巴组织细胞增生症 (HLH) 是一种描述患有严重全身性过度炎症的患者的综合征。特征包括持续发热、血细胞减少、肝脾肿大和典型 HLH 生物标志物升高。患者可出现肝炎、凝血功能障碍、肝功能衰竭、中枢神经系统受累、多器官功能衰竭和其他表现。该综合征的死亡率很高。越来越多的人认识到，虽然 HLH 可以适当地用作广泛的总结诊断，但许多儿科患者实际上患有越来越多的遗传疾病，这些疾病可能会并发 HLH 综合征。HLH 是典型和常见表现的经典遗传病包括家族性 HLH 基因（PRF1、UNC13D、STXBP2、STX11）的致病性变化，几种颗粒/色素异常基因（RAB27A、LYST、AP3B1）、X 连锁淋巴组织增生性疾病基因（SH2D1A、XIAP）和其他基因，如 NLRC4、CDC42 和 EBV 易感性疾病。在许多其他遗传疾病中，HLH 是该疾病的罕见并发症，而不是直接由遗传缺陷引起的疾病的突出表现，包括其他原发性免疫缺陷和先天性代谢缺陷。HLH 也可能发生在患有潜在风湿病或自身炎症性疾病的患者中，并且在这些情况下通常被称为巨噬细胞激活综合征。此外，HLH 可以在感染或恶性肿瘤期间在没有已知（或尚未确定）遗传易感性的患者中发展。