Hemophagocytic Lymphohistiocytosis in Adults (aHLH): Results from the German HLH Registry
Authors: Birndt Sebastian , Schenk Thomas , Brunkhorst Frank M. , Maschmeyer Georg , Rothmann Frank , Weber Thomas , Müller Markus , Panse Jens P. , Schroers Roland , Braess Jan , Frickhofen Norbert , Janka Gritta , Lehmberg Kai , Hochhaus Andreas , Ernst Thomas , La Rosée Paul 
Published: October 2019

Abstract
Introduction:
Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory syndrome caused by excessive immune activation leading to a life-threatening pro-inflammatory cytokine storm. HLH is not an entity of its own, but a clinical syndrome triggered by various conditions like infections, malignancy or autoimmune disorders. HLH pathogenesis is complex and still not fully understood. Contributing factors include immunosuppression (chemotherapy, long-term immunosuppressive therapy), cytokine release from tumor cells, imbalance between infected and immune effector cells as well as genetic predisposition. Despite improved HLH-specific therapy (adapted components from the pediatric HLH-1994 protocol), prognosis is still poor among adult HLH patients. Due to the lack of data on adult HLH in Germany, a national multicenter registry (http://www.hlh-registry.org/) was initiated.
Methods:
Patients (pts) with proven or suspected HLH were registered by 35 institutions across Germany from August 2010 to July 2016. Both HLH-2004 diagnostic criteria and the HScore (www.saintantoine.aphp.fr/score/) were used to confirm HLH diagnosis. To characterize adult HLH patients, data referring to underlying disease, treatment, outcome, clinical manifestations and laboratory findings were recorded. Where available, patient samples were tested for mutations of the perforin gene PRF1 by standard Sanger sequencing.
Results:
A total of 125 pts (48 female) were enrolled in our registry, of whom 105 pts either fulfilled diagnostic criteria according to HLH-2004 diagnostic guidelines (n=96) or met at least 4 out of 8 criteria and reached HLH-probability of over 90 % in the HScore (n=9). Among these 105 pts, n=38 (36 %) were female and n=67 (64 %) male. Median age at diagnosis was 49 years (range 17 - 81). Trigger diseases were in line with the literature, with infections (n=34) and malignancy (n=40) being most frequent (Table 1). Patients show a wide spectrum of underlying conditions, i.e. allogeneic stem cell transplantation (alloSCT) or HLH-mimicking diseases due to cytokine release in response to blinatumomab therapy. Late onset hereditary HLH was found in 3 pts (XLP-1 and -2 respectively in EBV-coinfected pts, one pt with perforin mutation - see below). 22 of 105 patients (21 %) were tested for PRF1 mutations. A compound heterozygous PRF1 A91V/Q405X mutation was identified in one pt presenting with NK/T-cell lymphoma. Heterozygous PRF1 A91V mutations were found in 2 pts with B-cell lymphoma and HLH following alloSCT respectively, in one case with available buccal swab DNA to prove germline origin of the mutation. Table 2 summarizes clinical and laboratory findings in the cohort. A median ferritin value of 32,000 µg/L underlines the importance to evaluate pts with highly elevated ferritin with respect to potential HLH diagnosis. Apart from fever and splenomegaly, clinical presentation frequently comprised hepatomegaly, liver failure, hyperbilirubinemia, renal failure, lung involvement like ARDS, or bleeding. Treatment included steroids in the vast majority of pts (n=89), often combined with i.v. immunoglobulins (n=47) and etoposide (n=49). After a median follow up time of 164 days, 48/97 pts (49.5 %) were alive, 8 pts were lost to follow up. Survival analysis revealed median overall survival of 454 days (Figure 1a). Comparing malignancy-associated HLH and HLH after alloSCT with infection- and autoimmune-associated HLH or HLH due to unknown triggers, survival was significantly poorer in the malignancy/alloSCT group (Figure 1b).
Conclusions:
HLH trigger conditions in adult patients in Germany are in accordance with published case series. Outcome in adult HLH is still poor, with malignancy-associated and HLH after alloSCT showing the worst prognosis. Diagnostic vigilance and early treatment is a prerequisite for improving outcome of adult HLH. In particular, high ferritin values should raise suspicion of HLH.

Disclosures
Hochhaus: Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; ARIAD: Honoraria, Research Funding.