Hemophagocytic lymphohistiocytosis in kidney transplantation: a call for heightened vigilance.

Hemophagocytic lymphohistiocytosis is a rare, severe, and potentially fatal disease, mainly encountered in individuals with immunologic diseases. Early diagnosis and prompt intervention may be life-saving. Herein, we report a case of a 52-year-old man who had undergone kidney transplantation nine years previously, presenting with persistent fever of unknown origin and graft function impairment. Despite receiving broad-spectrum antimicrobials and undergoing an exhaustive work-up for infectious, autoimmune, and oncologic diseases, he developed pancytopenia, hepatosplenomegaly, and respiratory failure. A bone marrow biopsy revealed florid hemophagocytosis, hyperferritinemia, hypertriglyceridemia, elevated serum soluble CD25, and cytopenia. These findings fulfilled seven of the Hemophagocytic lymphohistiocytosis 2004 criteria. High dose dexamethasone induced a partial, transitory response and lowered the fever, but multiorgan failure progressed, and the patient died three weeks after ICU admission. This case underscores that hemophagocytic lymphohistiocytosis should be considered whenever kidney transplant recipients develop unexplained fever, cytopenia, and hyperferritinemia, and suggests that early bone marrow evaluation with targeted immunomodulation may improve outcomes in this vulnerable population.