Successful Everolimus Treatment of Kaposiform Hemangioendothelioma With Kasabach-Merritt Phenomenon: Clinical Efficacy and Adverse Effects of mTOR Inhibitor Therapy.

Kasabach-Merritt phenomenon (KMP) is a life-threatening consumptive coagulopathy associated with underlying kaposiform hemangioendothelioma (KHE) in infancy. We describe the case of a 3-month-old girl with KHE complicated by KMP who responded dramatically to treatment with everolimus, a mechanistic target of rapamycin (mTOR) inhibitor. Immunohistochemical expression of mTOR was found in the KHE biopsy specimens, which may explain the improvement of KMP and reduction in KHE tumor size with mTOR inhibitor treatment. This effective use of everolimus may shed light on the emerging role of mTOR signaling in the development and pathogenesis of KHE and KMP.