Abstract
The leukemoid reaction (LR) is reported to be caused by severe stress conditions such as infection, malignancies, intoxication, severe hemorrhage, or acute hemolysis; this condition is attributed to a very severe prognosis. Some reports have suggested that the LR was associated with a systemic stress response. A 36-year-old man who required mechanical circulatory support (MCS), including veno-arterial extracorporeal membrane oxygenation and Impella 5.5 due to severe heart failure, was transferred to our hospital. He showed a markedly elevated WBC count and died of multiple organ failure. The autopsy revealed the possibility that leukocytosis might have been due to an LR; however, the cause of the cardiac failure was unknown. To the best of our knowledge, this study is the first to report a rare case of LR in a patient with severe heart failure requiring MCS.