Features, Treatment, and Outcomes of Macrophage Activation Syndrome in Childhood‐Onset Systemic Lupus Erythematosus

Objective To describe the features and treatment of macrophage activation syndrome (MAS) in a single‐center cohort of patients with childhood‐onset systemic lupus erythematosus (SLE), and to compare childhood‐onset SLE manifestations and outcomes between those with and those without MAS. Methods We included all patients with childhood‐onset SLE followed up at The Hospital for Sick Children from 2002 to 2012, and identified those also diagnosed as having MAS. Demographic, clinical, and laboratory features of MAS and SLE, medication use, hospital and pediatric intensive care unit (PICU) admissions, as well as damage indices and mortality data were extracted from the Lupus database. Student's t‐tests and Fisher's exact tests were used to compare continuous and categorical variables, respectively. We calculated incidence rate ratios of hospital and PICU admissions comparing patients with and those without MAS, using Poisson models. Kaplan‐Meier survival analysis was used to examine the time to disease damage accrual. Results Of the 403 patients with childhood‐onset SLE, 38 (9%) had MAS. The majority (68%) had concomitant MAS and SLE diagnoses. Fever was the most common MAS clinical feature. The frequency of renal and central nervous system disease, hospital admissions, the average daily dose of steroids, and time to disease damage were similar between those with and those without MAS. We observed a higher mortality rate among those with MAS (5%) than those without MAS (0.2%) (P = 0.02). Conclusion MAS was most likely to develop concomitantly with childhood‐onset SLE diagnosis. The majority of the MAS patients were successfully treated with corticosteroids with no MAS relapses. Although the numbers were small, there was a higher risk of death associated with MAS compared to SLE without MAS.