Macrophage Activation Syndrome in MIS-C.

BACKGROUND

Multisystem inflammatory syndrome (MIS-C) represents a diagnostic challenge because of its overlap with Kawasaki disease, Kawasaki disease shock syndrome, and toxic shock syndrome. Macrophage activation syndrome (MAS) is a frequently fatal complication of various pediatric inflammatory disorders and has been reported in MIS-C. Early diagnosis and prompt initiation by immune modulating therapies are essential for effectively managing MAS.

METHODS

We conducted a retrospective study to determine the frequency, natural history, diagnostic metrics, treatment, and outcome of MAS in MIS-C within a large cohort of patients across 84 Latin American centers in 16 countries. We compared the clinical and laboratory characteristics between patients with and without MAS.

RESULTS

Among 1238 patients with MIS-C, 212 (17.1%) fulfilled MAS criteria. Gastrointestinal and neurologic manifestations were more frequent in cases where MIS-C was complicated by MAS. Patients presenting with MIS-C complicated by MAS had a mortality rate of 12%, which was higher than those without it. Mortality was associated with MAS, seizures, arthritis, and shock. A ferritin or erythrocyte sedimentation rate ratio of >18.7 exhibited a sensitivity of 88.2% and a specificity of 75% in diagnosing MAS in MIS-C.

CONCLUSIONS

MAS in MIS-C patients is associated with increased morbidity and mortality rates in the largest MIS-C Latin American cohort. Early recognition and appropriate management are crucial in improving patient outcomes and reducing mortality rates.