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What

Kasabach-Merritt Syndrome is a disorder that is characterized by visible, aggressive hemangiomas (collection of abnormal blood vessels) and thrombocytopenia, or low platelet levels. The hemangiomas associated with Kasabach-Merritt syndrome grow rapidly and can predispose an affected child to significant bleeding through the consumption of platelets and clotting factors.

Who

Kasabach-Merritt Syndrome does not favor a particular race or ethnicity and affects males and females equally. The incidence of this condition is unknown however among children with hemangiomas, it is estimated to occur in only 0.3% of cases. This syndrome is usually diagnosed during infancy, but prenatal and adult diagnoses have also been made.

Signs and Symptoms

Those diagnosed with Kasabach-Merritt Syndrome typically have the following symptoms.

• Hardened, brownish-red or purplish lesions on the skin that may be painful and are usually on the trunk, arms and shoulders, legs, neck, and face. These lesions will spread quickly and may take a long time to resolve. In many cases, the lesions do not fully resolve.
  
• Hemangiomas located in internal organs such as the liver, spleen, or gastrointestinal tract that can lead to intestinal bleeding.
  
• Prolonged bleeding.

Possible Causes

The exact cause of Kasabach-Merritt Syndrome is not known, but it is thought to occur only in certain types of hemangiomas known as Kaposi hemangioendotheliomas and tufted angiomas. These subtypes grow rapidly and trap platelets within the walls of these abnormal blood vessels. The lack of platelets in the circulation may cause further problems when the child bleeds because there are not enough platelets to stop the bleeding in a timely manner.

Diagnosis

The diagnosis of Kasabach-Merritt Syndrome is made through physical examination, laboratory tests, tissue biopsy, and imaging of the hemangiomas. A complete blood count will indicate low levels of platelets, low levels of fibrinogen (which indicates that there is active consumption of an important protein involved in clotting), and high levels of d-dimers and fibrin split products (which indicates that clots in the body are being dissolved). Tissue biopsy will show abnormalities in the formation of blood vessels. Imaging of the lesion through magnetic resonance (MR), computed tomography (CT), or ultrasound can determine the dimensions of the lesions and detect lesions in other internal organs.

Treatment

There is no standard treatment for Kasabach-Merritt Syndrome. Treatment will vary according to the number of lesions, their anatomic location, and blood platelet levels. If the child is found to have extremely low levels of platelets (less than 20,000/uL) and other important clotting proteins, a transfusion will be needed. Fibrinogen, the protein critical to clot formation, can also be transfused. Surgical intervention has been successful in single skin lesions and multiple lesions of the liver and spleen. However, there must be careful monitoring before, during, and after the surgery because the child’s clotting ability is compromised. If the limbs are affected, compression therapy, in which pressure is placed upon the lesions, is helpful in reducing the spread of the lesion. If a certain blood vessel is known to be the cause of the hemangioma, it may be possible to stop the circulation in that vessel through vascular embolization, which creates a blockage in the vessel to stop blood from flowing through it. Medications used to control Kasabach-Merritt Syndrome include corticosteroids, interferon-alpha, and chemotherapeutic agents. Corticosteroids increase platelet counts. Interferon-alpha and chemotherapeutic agents are used to decrease the formation of new blood vessels within the hemangioma. Radiation therapy has also been used, but is generally not recommended as the initial treatment.

Prognosis

Kasabach-Merritt Syndrome is a difficult disorder to treat. Because of its tendency to occur early in life, about 20-30% of those afflicted with this disorder can die from complications. There must be close monitoring of the hemangiomas and platelet levels to minimize these complications.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Hemangioma Newsline
This is the newsletter of the National Organization of Vascular Anomalies, which provides a wide variety of resources, ranging from a physician listing to support services.

Platelet Disorder Support Association
This website is full of educational materials, stories about children with platelet disorders, and discussions groups for teens and adults.

Hemangiomas and Vascular Anomalies:
This is an educational website with plenty of pictures and explanations of birthmarks, including hemangiomas.

Google Search for Kasabach-Merritt Syndrome

References and Sources

Krafchik BR, Hendricks LK, Faguet G, and Kuthiala S (2003). Kasabach-Merritt Syndrome. www.emedicine.com/med/topic1221.htm Schrier SL (2004). Extrinsic nonimmune hemolytic anemia due to mechanical damage: Fragmentation hemolysis and hypersplenism. UpToDate. Hall GW (2001). Kasabach-Merritt syndrome: pathogenesis and management. British Journal of Haematology. 112:4, p. 851-862.