Emapalumab in Children with Primary Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome comprising familial/genetic HLH (FHL) and secondary HLH. In the HLH-94 study, with an estimated 5-year probability of survival (pSu) of 54% (95% confidence interval, 48%-60%), systemic therapy included etoposide, dexamethasone, and, from week 9, cyclosporine A (CSA). Hematopoietic stem cell transplantation (HSCT) was indicated in patients with familial/genetic, relapsing, or severe/persistent disease. In HLH-2004, CSA was instead administered upfront, aiming to reduce pre-HSCT mortality and morbidity. From 2004 to 2011, 369 children aged <18 years fulfilled HLH-2004 inclusion criteria (5 of 8 diagnostic criteria, affected siblings, and/or molecular diagnosis in FHL-causative genes). At median follow-up of 5.2 years, 230 of 369 patients (62%) were alive (5-year pSu, 61%; 56%-67%). Five-year pSu in children with (n = 168) and without (n = 201) family history/genetically verified FHL was 59% (52%-67%) and 64% (57%-71%), respectively (familial occurrence [n = 47], 58% [45%-75%]). Comparing with historical data (HLH-94), using HLH-94 inclusion criteria, pre-HSCT mortality was nonsignificantly reduced from 27% to 19% (P = .064 adjusted for age and sex). Time from start of therapy to HSCT was shorter compared with HLH-94 (P =020 adjusted for age and sex) and reported neurological alterations at HSCT were 22% in HLH-94 and 17% in HLH-2004 (using HLH-94 inclusion criteria). Five-year pSu post-HSCT overall was 66% (verified FHL, 70% [63%-78%]). Additional analyses provided specific suggestions on potential pre-HSCT treatment improvements. HLH-2004 confirms that a majority of patients may be rescued by the etoposide/dexamethasone combination but intensification with CSA upfront, adding corticosteroids to intrathecal therapy, and reduced time to HSCT did not improve outcome significantly.

Interferon-γ (IFNγ) is the pivotal mediator in murine models of primary haemophagocytic lymphohistiocytosis (pHLH). Given the similarities between primary and secondary HLH (sec-HLH), including macrophage activation syndrome (MAS), we investigate the involvement of the IFNγ pathway in MAS by evaluating levels of IFNγ and of the induced chemokines, and their relation with laboratory parameters of MAS in systemic juvenile idiopathic arthritis (sJIA) patients with MAS and in a murine MAS model.

We retrospectively studied the incidence of familial hemophagocytic lymphohistiocytosis (FHL) in children during the 16-year period 1971-86. First, all departments of pediatrics, pathology, and infectious diseases were enquired for children with FHL or disorders resembling FHL. Secondly, the causes of death of all children who died during the study period in Sweden (n = 19,542) were also investigated. Files and histological specimens were further studied in selected children. By using a set of inclusion/exclusion criteria, we found 32 children with FHL. The incidence was 1.2/1,000,000 children per year. One child per 50,000 live borns developed FHL during this period. The sex ratio was close to 1:1. Prominent early clinical signs were fever (91%), splenomegaly (84%), hepatomegaly (90%), rash (43%), and lymph node enlargement (42%). Neurological symptoms, which developed in 47%, could totally dominate the clinical picture and develop prior to other symptoms and signs. Common laboratory findings were pancytopenia, hypertriglyceridemia, hypofibrinogenemia, elevated serum transaminases, hyperbilirubinemia, hyponatremia, hypoalbuminemia, and a moderate spinal fluid pleocytosis. Chest X-ray often revealed mostly discrete pulmonary infiltrates. FHL is an underdiagnosed disease and in only 11/32 children was diagnosis made during their lifetime. It is important to be aware of the disorder as potential therapy now exists.