Systemic onset juvenile idiopathic arthritis (SoJIA) is the most common cause of MAS. MAS in other rheumatic illnesses occurs in the setting on unbridled inflammation. In both SoJIA and uncontrolled rheumatic disease the patient is liable to have high WBC counts and high platelet counts. Bone marrow suppression which is one of the pathognomic features of MAS would be picked up very late if absolute cut off values were utilized. Kelly et al used the same arguments in their review to suggest that in MAS/Reactive hemophagocytic lymphohistiocytosis(ReHLH), the trend of change in laboratory parameters would be more useful than absolute cut offs. Hence the investigators propose new candidate criteria which are based on trends of laboratory parameters and seek to determine their utility in comparison to absolute cut offs of HLH or Ravelli criteria. The investigators also wanted to determine that among the Ravelli criteria and HLH-2004 criteria, which were fulfilled earlier in patients diagnosed as having MAS.