C50-22 When Sepsis Isn’t Sepsis: A Case of Fatal Secondary Hemophagocytic Lymphohistiocytosis

Abstract Introduction Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome caused by uncontrolled immune activation leading to cytokine storm, cytopenias, and multiorgan failure. Laboratory findings include hyperferritinemia, elevated triglycerides, hypofibrinogenemia, and increased soluble IL-2 receptor levels are characteristic, but not specific. In adults, secondary HLH frequently mimics severe sepsis, and although its prevalence remains uncertain recent studies have estimated mortality rates of approximately 30% to 40% within the first two months of diagnosis, demonstrating the importance of early diagnosis and treatment.1-4 Case Presentation A 55-year-old man with hypertension, hyperlipidemia, peripheral vascular disease, neuropathy, and chronic kidney disease presented with five days of pleuritic chest pain, abdominal pain, chills, and dyspnea. On admission, he was hypoxic, tachycardic, and normotensive. Laboratory results showed acute kidney injury, mild anemia, thrombocytopenia, elevated inflammatory markers, and markedly elevated D-dimer. Infectious workup was negative. Despite broad-spectrum antibiotics, the patient developed worsening hypoxemia and progressive cytopenias, ultimately requiring intubation. Ferritin was markedly elevated at 11,878 ng/mL, and serum soluble IL-2 receptor levels were also increased, raising strong concern for HLH. Bone marrow biopsy was performed demonstrating a markedly hypercellular marrow with no evidence of malignancy, infection, or blast proliferation. Flow cytometry demonstrated 1% CD5+ monoclonal B-cell population, and cytogenetics revealed a normal karyotype. Given these findings, high-dose corticosteroids and etoposide were initiated for presumed HLH. Despite aggressive therapy, the patient developed refractory shock and expired. Autopsy revealed cardiomegaly, pulmonary edema, hepatic discoloration, and diffuse hemophagocytosis in the bone marrow, liver, and spleen, confirming HLH as the cause of death. Discussion This case highlights the diagnostic complexity of HLH, which often masquerades as septic shock. Key distinguishing features include cytopenias, hyperferritinemia, elevated soluble IL-2 receptor, and absence of an identifiable infectious source.5-7In adults, triggers often include infection, autoimmune disease, or malignancy; in this case, the presence of CD5+ monoclonal B-cell clone suggests the possibility of a lymphoproliferative driver.8,9Despite prompt recognition and initiation of etoposide-based therapy, the patient’s course underscores the aggressive nature of HLH once multiorgan failure develops. Clinicians should have a high suspicion for HLH in patients with sepsis-like syndromes that are unresponsive to conventional therapy, as prompt hematology consultation and initiation of immunosuppression have shown favorable outcomes and improved mortality.9 This abstract is funded by: None