Rationale and justification:-The HLH disorders are diagnosed using the HLH criteria. However as pointed out by Kelly et al9 and Ravelli et al10 use of this criteria to diagnose patients with MAS (i.e. Reactive HLH) would lead to a unacceptable loss of sensitivity and significant delay. Some components of the HLH criteria such as Soluble NK cell activity, CD-25 values above normal for age, and molecular diagnosis consistent with HLH are neither practical nor feasible in most clinical settings for a majority of rheumatology patients.