Post‐hematopoietic stem cell transplant hemophagocytic lymphohistiocytosis or an impostor: Case report and review of literature

<jats:title>Abstract</jats:title><jats:p>HLH occurring after HSCT is a relatively rare disease. Many conditions may mimic or trigger <jats:styled-content style="fixed-case">HLH</jats:styled-content> in post‐<jats:styled-content style="fixed-case">HSCT</jats:styled-content> period (eg, cytokine release syndrome, engraftment syndrome, graft rejection/failure, acute graft‐vs‐host disease, infections systemic inflammatory response syndrome/sepsis, and thrombotic microangiopathy). Moreover, this period is usually marked by febrile illness, cytopenia, and a “cytokine storm” leading to elevation of inflammatory biomarkers like ferritin and <jats:styled-content style="fixed-case">sCD</jats:styled-content>25. These parameters overlap with the diagnostic criteria for <jats:styled-content style="fixed-case">HLH</jats:styled-content>. Such confounding factors make the management of post‐<jats:styled-content style="fixed-case">HSCT HLH</jats:styled-content> quite challenging. We illustrate this critical issue with case report of a patient who was diagnosed with <jats:styled-content style="fixed-case">HLH</jats:styled-content> after allogeneic <jats:styled-content style="fixed-case">HSCT</jats:styled-content> for <jats:styled-content style="fixed-case">tAML</jats:styled-content>. He received <jats:styled-content style="fixed-case">MP</jats:styled-content> and CsA for <jats:styled-content style="fixed-case">HLH</jats:styled-content> but <jats:styled-content style="fixed-case">VP</jats:styled-content>‐16 was not administered due to fear of severe myelosuppression. Fortunately, he responded well to treatment and remains in remission to date. We recommend caution while using <jats:styled-content style="fixed-case">HLH</jats:styled-content>‐94/<jats:styled-content style="fixed-case">HLH</jats:styled-content>‐2004 guidelines for the diagnosis and management of post‐<jats:styled-content style="fixed-case">HSCT HLH</jats:styled-content>. In this article, we pinpoint these issues with a brief review of all the pediatric cases and clinical studies of post‐<jats:styled-content style="fixed-case">HSCT HLH</jats:styled-content> along with a critical evaluation of its various diagnostic criteria. Finally, based on the limitations of current diagnostic criteria, we suggest a need for formulating disease‐specific diagnostic criteria for post‐<jats:styled-content style="fixed-case">HSCT</jats:styled-content> HLH.</jats:p>