Background/Purpose:

Systemic onset juvenile idiopathic arthritis (SoJIA) is a rare autoinflammatory disorder comprising only 10% of JIA. Macrophage activation syndrome (MAS), an excessive and uncontrolled immune expansion, can develop within the setting of SoJIA. MAS is often overt but can be subclinical in up to 40% of patients. Early recognition of MAS is imperative, as the mortality rate despite treatment is high. Unfortunately, there is no pathognomonic finding for MAS, which can lead to delayed recognition. Use of the ratio between ferritin and erythrocyte sedimentation rate (ESR) has been reported to discern between flares of SoJIA, other febrile illnesses, and MAS.  The purpose of our project was to determine if utilization of the ferritin:ESR ratio at the onset of SoJIA could predict our patients with SoJIA who developed MAS.

Methods:

A single center, retrospective chart review of SoJIA patients was performed and data were extracted at the patientsÕ initial presentation.  Patients presenting initially to an outlying facility with incomplete records were excluded. The 2016 Ravelli criteria were used to identify those patients with MAS. SoJIA patients with and without MAS were compared using descriptive statistics. Binary logistic regression analysis was performed to identify predictors of MAS.

Results:

Eight of 30 patients met criteria for MAS during initial presentation. Laboratory analysis can be found in Table 1. Patients with MAS had significantly higher AST, CRP, and triglyceride levels with lower fibrinogen levels. Binary logistic regression did not indicate any significant predictive variables for MAS.

Conclusion:

No single laboratory value, including the ferritin to ESR ratio, was associated with the development of MAS at the initial presentation of SoJIA. These findings highlight the need for a comprehensive clinical and laboratory evaluation in all SoJIA patients to identify MAS.