Pediatric hemophagocytic lymphohistiocytosis in a tropical country: Results of a multicenter study in Thailand.

Background: Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening condition caused by genetic mutation or various triggers disturbing the immune system.

Methods: A multicenter retrospective study of pediatric patients with HLH receiving a diagnosis between January 2005 and December 2019 from three pediatric oncology centers was conducted to explore the clinical characteristics and determine prognostic factors associated with outcomes among Thai children.

Results: In all, 78 patients with HLH with a median age at diagnosis of 3.17 (range, .08-17.83) years were enrolled. The male to female ratio was 1.2:1. The most common type of HLH was infection-associated hemophagocytic syndrome (IAHS) (n = 59, 75%) of which Epstein-Barr virus was the most common pathogen. Thrombocytopenia, hyperbilirubinemia, and treatment response at weeks 2 and 8 after initiating treatment were associated with mortality. Platelet count <50,000 cells/mm was the only independent prognostic factor to define survival outcome (p-value .035). Two-year overall survival rate was 71.3% (95% confidence interval, 59.2%-80.3%). Survival rates between IAHS, malignant associated HLH, macrophage activation syndrome, and unspecific HLH did not significantly differ (p-value .571).

Conclusion: IAHS was the most common cause among pediatric HLH in Thailand. The outcomes of Thai children with HLH were comparable to those of developed countries. Platelet count <50,000 cells/mm was the only independent prognostic factor to define survival outcome.