Secondary Hemophagocytic Lymphohistiocytosis Triggered by Visceral Leishmaniasis Due to Leishmania infantum: A Case Report.

Background and Clinical Significance: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome characterized by uncontrolled activation of macrophages and cytotoxic lymphocytes. Secondary HLH is most commonly associated with infections, malignancies, and autoimmune disorders. Visceral leishmaniasis (VL) is an uncommon infectious trigger of HLH, and the considerable overlap in clinical manifestations frequently delays diagnosis. Early recognition of the infectious trigger is essential, because prompt targeted therapy may prevent the need for prolonged immunosuppressive treatment and substantially improve outcomes. Case Presentation: A 68-year-old livestock farmer from northern Greece presented with a one-month history of persistent fever, fatigue, and night sweats. Laboratory evaluation demonstrated pancytopenia, severe hyperferritinemia, hypertriglyceridemia, and elevated soluble interleukin-2 receptor (sCD25) levels. After extensive, relevant screening for other underlying etiologies, which proved to be negative, bone marrow examination revealed hemophagocytosis, while anti-Leishmania serology and polymerase chain reaction (PCR) analysis of bone marrow aspirate confirmed infection with Leishmania infantum. Treatment with liposomal amphotericin B along with intravenous dexamethasone resulted in rapid clinical and laboratory improvement. Serial ferritin and sCD25 measurements closely paralleled clinical recovery, supporting their potential usefulness as biomarkers of treatment response. The patient remained asymptomatic at one-month follow-up. Conclusions: Secondary HLH associated with VL is rare, but potentially fatal. Clinicians should maintain a high index of suspicion in patients presenting with prolonged fever, splenomegaly, cytopenia, and marked hyperferritinemia, particularly in endemic regions. Early diagnosis and prompt initiation of targeted therapy are associated with favorable outcomes.