EBV/CMV/Adeno-/Enterovirus blood PCR and consider other viral PCRs Stool virology/microbiology IL-10, IL-6 Triglycerides sCD25*
*consider full HLH screen if suggestive features present (e.g., splenomegaly, fibrinogen normal or low; ferritin >2,000 μg/l): Perforin-, SAP-, and XIAP-expression, NK cell degranulation and consider HLH-directed therapy (MDT). Here, PRF1 is linked to Splenomegaly.