Kasabach-Merritt phenomenon (illustration 1) is a rare, life-threatening condition in which a vascular tumor (tufted angioma or kaposiform hemangioendothelioma) traps and destroys platelets, which are a component of blood that helps clotting.

This condition is also associated with other abnormal clotting conditions in which there is excessive consumption of clotting factors. Kasabach-Merritt phenomenon does not occur in children with infantile hemangiomas.