2157: Optimizing the Diagnosis and Treatment of Kawasaki Disease-Associated Macrophage Activation Syndrome: A Clinical Cohort and Literature Analysis

Background/Purpose: Through a single-center retrospective cohort study and systematic literature review, we aimed to evaluate the applicability of current diagnostic criteria (HLH-2004/2009 and 2016 sJIA-MAS) for Kawasaki disease-associated macrophage activation syndrome (KD-MAS) and assess the clinical value of immunomodulatory treatment strategies.

Methods: A dual-cohort design was employed: (1) Retrospective analysis of pediatric patients treated at our institution from 2015 to 2025 who met the 2024 AHA Kawasaki disease diagnostic criteria and at least one MAS diagnostic criterion (HLH-2004/2009 or 2016 sJIA-MAS); (2) Systematic literature search for KD-MAS case reports. Data on demographic characteristics, clinical manifestations, biomarker dynamics, treatment responses, and outcomes were collected. Treatment efficacy was stratified and compared based on glucocorticoid dosage (Mann-Whitney U test).

Results: Analysis of 44 KD-MAS cases (22 from our center and 22 from literature) revealed an incidence rate of 0.6% (22/3,786) at our institution, with a male-to-female ratio of 2.1:1 and median age of 4.2 years. Diagnostically, 72.7% (32/44) met all diagnostic criteria, 93.2% (41/44) fulfilled the 2016 sJIA-MAS criteria, and 72.7% (32/44) met the HLH-2004/2009 criteria. All patients received IVIG, with 90% requiring additional immunomodulatory therapy. Among 13 patients treated with methylprednisolone alone at our center, no significant difference in CRP improvement was observed between high-dose (≥10 mg/kg/day, n=7) and low-dose (< 10 mg/kg/day, n=6) groups (P=0.23). The overall cure rate was 95% (39/41, excluding 3 lost-to-follow-up cases), with two fatal cases at our institution associated with treatment delay.

Conclusion: This study is the first to demonstrate the superior sensitivity of the 2016 sJIA-MAS criteria for KD-MAS diagnosis. Initial low-dose glucocorticoids (< 10 mg/kg/day) are effective for mild KD-MAS, but treatment escalation is warranted if no clinical improvement is observed. Treatment delay was identified as an independent risk factor for poor prognosis.