The primary purpose of this study is to determine whether giving injections of anakinra is a safe and well tolerated treatment to give as an adjunct to standard prescribed treatment for patients who are admitted to the hospital with signs of severe inflammation (macrophage activation syndrome) that is potentially life-threatening. Anakinra is a commercially available product (Kineret™) approved for the treatment of rheumatoid arthritis; it is a replica of a naturally occurring protein called Il-1 receptor antagonist (IL-1ra), made by humans to inhibit and regulate the action of interleukin-1 (IL-1). IL-1 is a mediator of inflammation that when generated in excess amounts by immune system cells can result in severe dysfunction of multiple organs that can be life-threatening. The specific primary objectives of the study are to determine if giving anakinra results in no increased infection complications or mortality. Additional data will be collected to determine whether anakinra administration results in any other unanticipated side effects in this setting, and the effects of anakinra administration on inflammation markers, the overall dose of steroids required to treat the inflammation, and the length of hospital stay.