Background: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening disease. Relapsed/refractory disease is the main cause of death. This study is aimed to determine the prognostic indicators for relapsed/refractory disease in childhood HLH (R/R HLH). Procedure: Infants and children under 18 years of age who were diagnosed with HLH according to HLH-2004 criteria, MAS-HLH criteria for rheumatologic diseases, or H-score undergoing treatment in Chiang Mai University hospital between 2010 – 2022 were included. Demographic data, clinical characteristics, and laboratory parameters were retrospectively reviewed. Results: Out of 86 childhood HLH cases, 30 patients (34.9%) experienced R/R HLH. All patients with primary HLH developed R/R HLH. The most common form of secondary HLH was infection-associated hemophagocytic syndrome (IAHS), comprising 43 cases. Of these, 37.2% had relapsed or refractory disease. Univariable analysis identified several potential risk factors for R/R HLH, including younger age, severe disease status, higher HLH-2004 criteria scores, higher H-scores, overt DIC, higher pSOFA scores, and increased levels of aspartate aminotransferase, total bilirubin, and direct bilirubin. Multivariable logistic regression analysis revealed that a pSOFA score of ≥ 8 and age < 3 years were independent risk factors for R/R HLH, with adjusted odds ratios of 6.35 (95% confidence interval [CI], 1.18 – 34.19; p = 0.032) and 3.62 (95% CI, 1.04 – 12.63; p = 0.044), respectively. Conclusions: Children with HLH who have a pSOFA score of ≥ 8, or are younger than 3 years, are at a higher risk of relapsed or refractory disease. Further evaluation of management strategies in this context is warranted.
