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.