Hemophagocytic Lymphohistiocytosis Complicated With Reversible Cardiomyopathy and Severe Sinus Node Dysfunction.

BACKGROUND: Hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammation syndrome causing multiorgan failure. While cardiac involvement is recognized, associated conduction-system abnormalities are exceedingly rare and poorly described. CASE SUMMARY: A 60-year-old male presented with fever, pancytopenia, and progressive shock, meeting diagnostic criteria for HLH. His clinical course was acutely complicated by transient cardiomyopathy and frequent episodes of sinus arrest. Following the initiation of HLH-directed therapy, the patient experienced a complete recovery of both systolic function and sinus node conduction by day 10. DISCUSSION: This case identifies severe sinus node dysfunction as a reversible manifestation of HLH-related cytokine storm. Prompt initiation of immunosuppressive therapy led to complete recovery of left ventricular function and sinus node activity, highlighting the reversible nature of the HLH-related myocardial injury. TAKE-HOME MESSAGE: This case highlights the importance of early identification of HLH-related cardiac involvement as it is critical to prevent irreversible damage and improve outcomes in these patients.