Hemophagocytic Lymphohistiocytosis: Potentially Underdiagnosed in Intensive Care Units.

Background: Hemophagocytic lymphohistiocytosis in adults (aHLH) is a rare life-threatening hyperinflammatory syndrome caused by excessive activation of macrophages and CD8+ T-cells. Due to the clinical overlap with severe sepsis, aHLH often remains undiagnosed resulting in poor outcome. Here, we present a retrospective study of incidence, clinical findings, and the outcome of aHLH in intensive care units (ICUs).

Methods: This retrospective analysis was performed at the university hospital Charité - Universitätsmedizin Berlin. We gathered data from 556 out of 46,532 patients admitted to our anesthesiological ICUs between 2006 and 2013, who had at least one plasma ferritin measurement during ICU treatment, and were at least 18 years old. Of these, 244 patients with ferritin at least 500 μg/L and available datasets of at least 4 HLH-2004 criteria were included. HLH-2004 diagnostic criteria and the recently published HScore were used. An aHLH expert team retrospectively reviewed the potential aHLH cases.

Results: Seventy-one of the included 244 patients died; 9 out of the 244 patients were retrospectively classified as aHLH of whom 4 patients had died (44.4%). Two of the 9 aHLH patients had been correctly diagnosed and had received specific aHLH treatment. Thus, 7 out of 9 patients (77.8%) remained undetected. ICU patients with at least 1 captured ferritin value and hyperferritinemia showed an aHLH rate of 3.7%, which rises up to 5.6% when only deceased patients are considered. Mortality in this selected cohort is 44.4%.

Conclusions: Overall, 7 out of 9 patients (77.8%) suffering from aHLH remained undiagnosed. Awareness of this life-threatening syndrome, especially in ICUs, should be raised. The inclusion of ferritin into the admission lab panel for ICU is warranted.Clinical trial registered with www.ClinicalTrials.gov (NCT02854943) on August 1, 2016. As this is a retrospective study, trial registration was after final data collection date.