KasabachMerritt

Kasabach-Merritt phenomenon, also known as Kasabach-Merritt syndrome or Kasabach-Merritt coagulopathy, is a rare but potentially life-threatening consumptive coagulopathy that occurs in association with certain vascular tumors, most commonly kaposiform hemangioendothelioma (KHE) and tufted angioma. It was described in infants by Kasabach and Merritt in the 1940s. The condition arises when the tumor traps and activates platelets and coagulation factors, leading to profound thrombocytopenia, hypofibrinogenemia, prolonged clotting times, and elevated D-dimer, with possible bleeding and anemia.

Clinically, patients present with rapidly enlarging, firm, violaceous lesions that may be surrounded by ecchymoses or purpura. The coagulopathy can worsen as the tumor grows, and bleeding may occur from the tumor or at other sites. Although most cases occur in infancy, Kasabach-Merritt phenomenon can be seen in older children with vascular tumors.

Diagnosis is based on the combination of a compatible vascular tumor and laboratory evidence of consumptive coagulopathy. Imaging, typically MRI or ultrasound, is used to define tumor extent and involvement of surrounding structures, and helps guide treatment. Differential diagnosis includes other infantile vascular tumors and coagulopathies.

Treatment requires a multidisciplinary approach focused on stopping the coagulopathy and reducing tumor burden. First-line therapies often include systemic corticosteroids and sirolimus, with vincristine, pulses of chemotherapy, or interferon used in some cases. Supportive care may involve careful management of platelets and fibrinogen, and interventional options such as embolization or surgery may be considered in select cases. The prognosis has improved with modern therapies, but the condition remains potentially fatal, underscoring the importance of early recognition and coordinated care.