Retrospective single-centre analysis of diagnostic approach to adult-onset haemophagocytic lymphohistiocytosis

Background: Haemophagocytic lymphohistiocytosis (HLH) is a rare disorder with a poor prognosis characterised by substantial immune activation leading to end-organ failure. In childhood, genetic defects that impair cytotoxic function of natural killer cells and T cells. (HLH) are often identified. In adults, clinical manifestations are similar to those observed in children but the aetiology is often unclear. Aims: To evaluate whether poor prognosis for adult HLH is in part due to lack of awareness of the disorder, which results in incomplete investigation and failure to implement timely treatment. Methods: We performed a retrospective case series of adult-onset HLH in a tertiary hospital in Australia. We evaluated clinical characteristics, treatment and outcome, and related these to application of standard diagnostic criteria for HLH. Results: In our centre, incomplete assessment of HLH criteria was common. Serum ferritin was the criterion most commonly assessed. Hyperferritinaemia ≥10 000 μg/L was highly sensitive in detecting patients with adult-onset HLH; however, the majority of patients who had hyperferritinaemia ≥10 000 μg/L did not have adult-onset HLH. Conclusion: The present study highlights the importance of comprehensive application of diagnostic criteria to improve accuracy and timelines of the diagnosis of adult onset HLH.