*Purpose: Hemophagocytic Lymphohistiocytosis (HLH) is a hyperinflammatory syndrome characterized by cytokine storm from the activated reticuloendothelial system. Due to the nonspecific presentation and overlap with other illnesses, diagnosis is often delayed. It has a very poor prognosis, with a 40-50% mortality rate. Reports in solid organ transplant (SOT) are meager. In this study, we aim to evaluate the incidence, triggers, and outcomes of HLH in SOT.

*Methods: We did a diagnosis-based database search of all the SOT performed at our center in the past ten years.

*Results: Seven SOT recipients with a diagnosis of HLH [Five Kidneys, one Liver, and one Heart] were identified. Induction agents were ATG in all Kidney recipients and IL-2 receptor antagonist for Liver and Heart transplant. Maintenance agents were Calcineurin Inhibitors and Myfortic. The median time to diagnosis post-transplant was 2 years [1-13]. All recipients were Caucasians, 72% male, and the median age of diagnosis was 50 years [28-72]. The presentation included fever, acute hypoxic respiratory failure, shock, altered mental status, hemiplegia, tremors, and hearing loss. Labs showed hyperferritinemia (8000-124,000 ng/mL), elevated Interleukin 2 receptor [1600-6500, normal 139-579 pg/mL], hypertriglyceridemia [613-765- normal less than 150mg/dL], transaminitis, coagulopathy, and pancytopenia. Bone marrow (BM) biopsy demonstrated hemophagocytosis in 72% of patients. This is consistent with previous reports where 25% could have a negative biopsy. The triggers for HLH were EBV positive PTLD (4 cases, EBV PCR 0.3-10 million IU/mL), CMV (PCR – 70 million IU/mL), Ehrlichia, and Clostridium difficile. Treatment modalities used were immunomodulatory agents (dexamethasone, anakinra, ruxolitinib), PTLD guided treatments (R-EPOCH, rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin), and treatment of inciting illness (doxycycline for the Ehrlichiosis and ganciclovir/foscarnet for CMV]. Both patients who died were Kidney transplant and died within a month of diagnosis. The first patient was a 72-years old male with CMV titers of 70 million. He initially responded to dexamethasone, anakinra, and ruxolitinib but later developed multi-organ failure. The second patient was 59-years old with EBV positive PTLD (PCR – 10 million) and was treated with R-EPOCH and anakinra. Overall, the mortality was 28%, which is less than previously reported studies and could be due to early treatment initiation.

*Conclusions: Our case-series suggest that severe infections especially EBV positive PTLD, and elderly recipients have a poor prognosis. Early empiric dexamethasone improves outcomes and should be considered if HLH is suspected without waiting for the BM biopsy. The development of a registry for SOT with HLH would enhance our understanding of this syndrome.

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