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Kasabach–Merritt phenomenon (KMP) is a rare but life-threatening consumptive coagulopathy associated with certain vascular tumors.

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Characterized by the triad:

1. Vascular tumor (classically Kaposiform hemangioendothelioma (KHE) or tufted angioma).
2. Severe thrombocytopenia (due to platelet trapping within the tumor).
3. Consumptive coagulopathy (hypofibrinogenemia, elevated D-dimer, prolonged PT/aPTT).

Etiopathogenesis

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Platelets become sequestered and activated within abnormal vascular channels of the tumor.

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• Platelet consumption → severe thrombocytopenia.
• Secondary fibrinolysis and coagulation activation → hypofibrinogenemia, DIC-like picture.

Commonly associated tumors:

• Kaposiform hemangioendothelioma (KHE) (most common).
• Tufted angioma .
• Less commonly, Infantile hepatic hemangioendothelioma (IHE) .

Clinical Features

• Presents in infants and young children.
• Rapidly enlarging vascular lesion (cutaneous or visceral).
• Skin: purplish, firm, ill-defined lesion (not compressible like infantile hemangiomas).

![Classic clinical case of Kaposiform hemangioendothelioma with Kasabach-Merritt phenomenon (KMP) diagnosed in a 5-week-old patient. Extension of cutaneous involvement. Photos presented with mother’s permission. (A) At the peak of activity of KMP (day 4)—patient with purpura, edema, irregular margins, and extensive size. (B) After 3 weeks of treatment, the cutaneous component improved significantly. (C) After 2 months of therapy with sirolimus and steroids, complete resolution of the cutaneous component was achieved.

Mahajan P, Margolin J, Iacobas I. Kasabach-Merritt Phenomenon: Classic Presentation and Management Options. Clinical Medicine Insights: Blood Disorders. 2017;10. doi:10.1177/1179545X17699849](attachment:24ccc873-e1cf-472b-b8b1-672b084c0c1b:10.1177_1179545x17699849-fig2.jpg)

Classic clinical case of Kaposiform hemangioendothelioma with Kasabach-Merritt phenomenon (KMP) diagnosed in a 5-week-old patient. Extension of cutaneous involvement. Photos presented with mother’s permission. (A) At the peak of activity of KMP (day 4)—patient with purpura, edema, irregular margins, and extensive size. (B) After 3 weeks of treatment, the cutaneous component improved significantly. (C) After 2 months of therapy with sirolimus and steroids, complete resolution of the cutaneous component was achieved.

Mahajan P, Margolin J, Iacobas I. Kasabach-Merritt Phenomenon: Classic Presentation and Management Options. Clinical Medicine Insights: Blood Disorders. 2017;10. doi:10.1177/1179545X17699849