Kasabach-Merritt phenomenon (KMP)
Kasabach-Merritt phenomenon a severe coagulopathy disorder characterized by severe thrombocytopenia (platelet count < 50,000/mm3), elevated D-dimer, hypofibrinogenemia and prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT)1. Anemia may be present especially if bleeding symptoms. KMP is known to occur as an association with specific vascular tumors - Kaposiform hemangioendothelioma (KHE) or Tufted Angioma (TA). KHE is a rare, life-threatening vascular tumor and frequently presents with KMP in up to 70% of cases2. The KHE lesion most commonly presents as an enlarging, firm mass with red-purple discoloration if the skin is involved, typically presenting shortly after birth or during early childhood. When associated with KMP it is generally rapidly enlarging, warm to touch and very purpuric in coloration. Not all KHE have cutaneous involvement and diagnosis may be delayed2. Often patients without cutaneous involvement present with signs of thrombocytopenia and mucocutaneous bleeding. Intrathoracic and retroperitoneal KHE may be at higher risk for KMP as these lesions are often very large and expansive1-3. The etiology of the coagulopathy in KHE is not well-understood. It likely involves platelet trapping within the vascular lesion followed by activation of the platelets and further platelet aggregation3,4. This ultimately leads to activation of the coagulation cascade and consumption of factors. Intralesional thrombi and subsequent hemorrhage leads to the clinical findings of “growth”, deepening of color and warmth of the lesions1.