INTRODUCTION: Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory syndrome that can lead to early death from multiple organ failure. In secondary HLH, etiological treatment is an emergency, but sometimes impossible until complementary results (microbiology, histology) are available. A "bridge to etiological treatment" with anti-inflammatory drugs (anti-JAK, anti-cytokines or etoposide) is then essential. This study was conducted to determine the right time to start such treatment.

METHODS: We conducted a retrospective study at the University Hospital of Marseille on ultra-selected (HS score above 215, probability of HLH = 95%) adult patients treated for secondary HLH in the intensive care unit (ICU).

RESULTS: Over a 10-year period, we included 23 patients (7 women, 16 men, 49 years (37-59)). The median HS score was 272 (250-294). 14 patients had infection-related HLH, 4 patients had lymphoma-related HLH and 2 patients had adult-onset Still's disease (AOSD). 7 patients died (30.4%), all of whom received invasive organ support (IOS = invasive mechanical ventilation, noradrenaline and/or renal replacement therapy). When comparing the 14 patients with IOS with the 9 others, we found no differences in terms of age, etiology, clinical-biological characteristics and HLH-directed therapy. The mortality rate was 0 in the group without IOS compared to 7 deaths (50%) in the IOS group (p = 0.02).

CONCLUSIONS: In secondary HLH, symptomatic anti-inflammatory treatment (awaiting etiological treatment) is an absolute emergency to stop macrophage and/or lymphocyte activation before organ failure occurs. A drastic increase in ferritin and a decrease in platelets could be biological warning signs.