Kasabach-Merritt Syndrome Clinical Presentation

Updated: Sep 12, 2022
  • Author: Alexandra C Cheerva, MD, MS; Chief Editor: Hassan M Yaish, MD  more...
  • Print


Visible cutaneous blue, violaceous, or reddish-brown lesions are often the presenting features in patients with Kasabach-Merritt syndrome (KMS). [6] Most lesions are located on the extremities. Some infants and older children with visceral lesions present with an enlarged abdomen. Those with hepatic kaposiform hemangioendotheliomas also may present with hepatomegaly or jaundice. These vascular lesions may continue to enlarge during the first 18 months of life.

The thrombocytopenia and consumption coagulopathy associated with KMS may not initially be severe. However, symptoms may worsen as the lesion enlarges and the infant grows. Affected infants may present soon after birth or may not come to medical attention for several months. Affected individuals rarely present as late as the second or third decade of life.

Petechiae, bruising, and frank bleeding may be the initial symptoms prompting medical treatment. The lesions may be painful.

The large volume of blood circulating through the lesion may cause high-output congestive heart failure in infants. [15] Cardiovascular compromise or collapse, petechiae, and bleeding may resemble acute overwhelming sepsis. When no cutaneous lesion is present, the physician must search for vascular lesions located in a visceral organ (eg, the spleen, liver, [16] or brain).

Some patients with diffuse cavernous kaposiform hemangioendothelioma (KHE) of a visceral organ may present with anemia, thrombocytopenia, coagulopathy, and bleeding, which may be misdiagnosed as immune thrombocytopenic purpura. [17]

The natural history of KHE is that of slow regression, with the lesion leaving a reddish-brown discoloration that often does not resolve completely. It is unknown what percentage of KHE lesions develop into KMS.


Physical Examination

A cutaneous vascular lesion is usually obvious, often appearing as a large irregular bruise (see the first image below). These lesions may occur anywhere on the body and may grow through the first 12-18 months of life, often circumscribed by widespread, overlying, shiny and dusky, purple skin. [18] Lesions of KHE (see the second image below), tufted angioma (TA), or a mixture of both present with a blue or reddish-brown discoloration and skin induration. When thrombocytopenia increases, a large violaceous, ecchymotic indurated mass forms.

Back of an arm showing the typical bruising associ Back of an arm showing the typical bruising associated with Kasabach-Merritt Syndrome.
Leg with a Kaposiform hemangioendothelioma, lesion Leg with a Kaposiform hemangioendothelioma, lesion associated with Kasabach-Merritt Syndrome.

Affected infants may exhibit petechiae, bruising, and bleeding. Bruising and ecchymoses may occur at distant sites. Internal lesions may present with only bruising and ecchymoses on the skin. The lesions are usually painful and tender. Aggressive infiltration with ulceration and infection is rare but can occur. Bleeding from thrombocytopenia and coagulopathy is observed both locally and, at times, distantly (ie, disseminated intravascular coagulation [DIC]).

Physical signs of high-output cardiac failure include tachycardia, feeding difficulty, and shock. Pallor may be evident in patients with significant anemia.



The clinical course of KMS is unpredictable, and effective treatment depends on control of the invasive tumor before secondary complications occur.

Various complications of KMS relate to the site of the vascular lesion. For example, hemangiomas of the chest that invade the thorax can compromise lung expansion and cause respiratory insufficiency.

Other complications that may be seen include the following:

  • Severe thrombocytopenia (platelet count < 5 X 109/L (< 5000/µL)

  • Ulceration and bleeding into the vascular lesion

  • Bleeding secondary to DIC and unresponsive to platelet transfusions (potentially fatal)

  • Toxicity from the agents used to treat KMS (eg, secondary malignancy from radiation therapy)

  • High-output cardiac failure (potentially fatal)

  • Infections from skin breakdown with sepsis