Relapse EBV-HLH and ANKL in an 8-Year-Old Patient:a Case report

Background: Hemophagocytic Lymphohistiocytosis (HLH) often arises as a hematologic complication of acute and chronic diseases. Identification of underlying disease is crucial for determining HLH prognosis. The global incidence of aggressive natural killer cell leukemia (ANKL), which is rare, aggressive, and lacks a distinctive immunophenotypic or molecular hallmark characteristic, is much rarer in children. Approximately 60–90% of ANKL co-occurs with HLH. The diagnosis of HLH may ignore the presence of ANKL. Therefore, identifying and treating ANKL in children with HLH is difficult. Case presentation: The case reports an 8-year-old male initially diagnosed with EBV-HLH and consented to the HLH-2004 regimen, but EBV-HLH returned. We found that the NK cell fraction increased in EBV-HLH. Finally, peripheral blood flow cytometry (FCM) was performed to diagnose ANKL. We strengthened the L-DEP regimen for EBV-HLH with methylprednisolone; and the SMILE regimen for ANKL. After haplo-HSCT, the patient endured for more than four years. Conclusions: It serves as a reminder that the increased NK cell fraction is an important clue for identifying ANKL in EBV-HLH; peripheral blood FCM is superior to bone marrow and other tissue sites with restricted laboratory testing for the diagnosis of ANKL.