2.1 Patient selection
After obtaining approval from the Institutional Research Board/Ethics
Committee (IRB/EC) of Chiang Mai University, a retrospective medical
record review was conducted for infants and children under 18 years
diagnosed with HLH according to the HLH-2004 criteria, the MAS-HLH
criteria for rheumatologic diseases, or the H-score. This study focused
on patients undergoing treatment at Chiang Mai University hospital
between 2010 and 2022. The patients exhibiting HLH-like illness but not
meeting the specified diagnostic criteria were excluded. Data collected
included demographic and clinical characteristics, HLH subtype, HLH-2004
criteria score4, H-score11, MAS-HLH
criteria5, 6, pediatric Sequential Organ Failure
Assessment (pSOFA) score12, modified ISTH-DIC
score13, 14, HLH severity based on the Histiocyte
Society guideline15, laboratory parameters, genetic
testing, bone marrow examination results, and pathology reports.
Relapsed HLH was defined as the active disease occurring post-remission
with standard HLH therapy, while refractory HLH was characterized by the
failure to achieve a response 2 weeks after initiating standard HLH
therapy. 15, 16 All diagnostic criteria and HLH
severity grading were included in Supplemental Table S1. The pSOFA score
and the modified ISTH-DIC score were presented separately in
Supplemental Table S2.