Kasabach-Merritt Phenomenon See Also... Request an Appointment Family Accommodations Billing Information Virtual Tours Handouts/Teaching Sheets Related Links Laser slide show Types of birthmarks Hemangiomas Vascular malformations PHACES syndrome Sturge-Weber syndrome The Kasabach-Merritt phenomenon (KMP), a complication of rapidly enlarging vascular lesion, is characterized by hemolytic anemia, thrombocytopenia and coagulopathy. Most cases can be seen in the first weeks of life. The vascular tumors that cause KMP are large, deep red-blue color, firm, grow rapidly, affect boys and girls equally and tend to grow for a longer period of time (two to five years). It now is clear that most patients with true Kasabach-Merritt phenomenon do not have hemangiomas of infancy, but rather other more aggressive proliferative vascular tumors. Kaposiform hemangioendotheliomas and tufted angiomas are the tumors most often associated with this phenomenon. They can be very serious, even fatal, and require aggressive and often many different types of treatment.