IL2 and hemophagocytic syndrome: In previous literature, it has been shown that higher ferritin at time of diagnosis as well as a slower rate of decrease in ferritin is associated with a poor prognosis and higher mortality.1,2 Although interleukin (IL)-2 level and natural killer (NK) cell activity are potentially more specific biomarkers of HLH, ferritin is more readily available and a high level can offer the first step to an earlier diagnosis of HLH.