# Haemophagocytic lymphohistiocytosis in critically ill adults: a single-centre retrospective ICU cohort study

## TL;DR

This study examines haemophagocytic lymphohistiocytosis in critically ill adults, finding high ICU mortality and significant organ support needs.

## Contribution

The study provides insights into clinical characteristics and outcomes of HLH in adult ICU patients over a 16-year period.

## Key findings

- ICU mortality for HLH patients was 65.1% with high rates of respiratory failure and sepsis.
- Ferritin levels were markedly elevated, with 93% exceeding 6,000 μg/l.
- Diagnostic scores like HScore showed no significant difference between survivors and non-survivors.

## Abstract

Haemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome characterised by uncontrolled immune activation and multi-organ dysfunction. Whilst initially described in paediatric populations, HLH is increasingly recognised in critically ill adults, often triggered by malignancies, infections, or autoimmune diseases.

This single-centre retrospective study analysed 43 adult patients with HLH admitted to the ICU between 2008 and 2024. Clinical characteristics, laboratory parameters, organ support requirements, and outcomes were assessed. Temporal trends in routine parameters surrounding HLH diagnosis were also evaluated.

The median age was 45 years (IQR: 33–60), and 65% were male. Respiratory failure (62.8%) and sepsis (41.9%) were the leading causes of ICU admission. Disease severity was high, with a median SOFA score of 14 (IQR: 11–17), and ICU mortality reached 65.1%. Invasive mechanical ventilation was required in 83.7% of patients, and continuous renal replacement therapy in 72.1%. Ferritin levels were markedly elevated, with a median peak of 25,045 μg/l (IQR: 12,771–94,586), with 93% of patients exceeding 6,000 μg/l. The median HScore was 245 (IQR: 210–273) and did not differ significantly between survivors and non-survivors (p = 0.64).

HLH in adult ICUs carries high mortality and demands extensive organ support. Existing diagnostic scores provide limited bedside guidance, highlighting the need for ICU-specific validation and improved prognostic markers.

Study infographic titled "Haemophagocytic Lymphohistiocytosis in the ICU." It shows cohort details: 43 patients, 65 percent male, average age 45, spanning 2008–2024. Triggers include infection (40%), hematologic disease (35%), autoimmune disease (7%), and idiopathic (18%). Severity indicators: SOFA score 14, ferritin 25,000 ng/mL, HScore 245. Outcomes: ICU mortality 65%, renal replacement therapy 72%, invasive mechanical ventilation 84%. Includes visual elements like a cytokine storm and dysregulated immune system depiction.