NORD is very grateful to Denise M. Adams, MD, Associate Professor, Department of Hematology/Oncology, Cincinnati Children's Hospital Medical Center, for assistance in the preparation of this report.
Synonyms of Kasabach-Merritt phenomenon
- Kasabach-Merritt syndrome
- thrombocytopenia with a vascular lesion
- No subdivisions found.
Kasabach-Merritt phenomenon (KMP) is a rare condition that is associated with a coagulopathy with features including profound thrombocytopenia (low platelets), hypofibrinogenemia (low fibrinogen), and anemia. This phenomenon is only associated with two rare vascular tumors: kaposiform hemangioendotheliomas and tufted angiomas. This condition can be life threatening secondary to the risk of bleeding and progression to DIC (disseminated intravascular coagulopathy).
Initially a vascular lesion is noted on the skin which can be firm, indurated and purpuric. Areas of petechiae (tiny red dots) can appear around the lesion or on other parts of the body. If the vascular lesion is internal, these petechiae can be seen on the skin. Bruising and spontaneous bleeding can also occur. These tumors are not hemangiomas. They usually present in young infants, less than three months of age, but have rarely been reported in older children. These tumors occur in the extremities, chest, neck, abdomen and pelvis. They infiltrate across tissue plans and can be aggravated by interventions, infection and trauma. When these tumors with KMP are internal such as in the pleural or retroperitoneum, they can cause significant morbidity and mortality. The morbidity and mortality is caused by bleeding.
The cause of Kasabach-Merritt phenomenon is unknown. It is believed to be secondary to sequestration or trapping of platelets into the tumor. These tumors are made up of abnormal endothelial cells (spindle cells) and also lymphatic malformation. It is unclear why the KMP occurs and if it is caused by the spindle cells or the lymphatic component.
Kasabach-Merritt phenomenon is a rare disorder that affects males and females equally The diagnosis is most often made during infancy but older children have been reported with this phenomenon. KHE and TA tumors can occur without KMP. The reason for this is still unknown and may be secondary to a smaller size of the tumor, an older age at presentation or other clinical features.
Symptoms of the following disorders can be similar to those of Kasabach-Merritt phenomenon. Comparisons may be useful for a differential diagnosis:
Large malformations such as venous or venous lymphatic lesions and multiple lesions can causes coagulopathies with low platelet counts and other coagulation proteins. This coagulopathy is not Kasabach-Merritt phenomenon.
The rare vascular tumors associated with Kasabach-Merritt phenomenon were misdiagnosed as hemangiomas in the past. Hemangiomas are benign tumors with endothelial proliferation which are usually not present at birth but proliferate and grow over a 4 to 6 month period of time and then stabilize and involute. Hemangiomas are not associated with any coagulopathy or thrombocytopenia.
Low platelets can be associated with other vascular tumors and malformations and this should not be classified at Kasabach-Merritt phenomenon
The diagnosis of Kasabach-Merritt phenomenon is based on the diagnosis of Kaposiform hemangioendothelioma/tufted angioma and this coagulopathy as noted above. If this diagnosis is suspected blood work including a CBC with differential and platelets, fibrinogen, D-dimer, PT, and PTT should be ordered. The best imaging modality to assess the extent of the lesion is a MRI with contrast. A biopsy will confirm the diagnosis.
There is no known standard of therapy for Kasabach-Merritt phenomenon. Medical management has included corticosteroids, interferon, chemotherapeutic agents such as vincrisitne, aspirin, and antiplatelet drugs such as Ticlopidine. Sometimes a combination of medications has been used. Other adjuvant therapies have included interventional embolization. If the lesion can be surgically removed that is the treatment of choice.
Patients diagnosed with these conditions need to be treated at multidisciplinary vascular anomaly centers.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:
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Contact for additional information about Kasabach-Merritt phenomenon:
Denise M Adams, MD
Professor of Clinical Pediatric Hematology Oncology
Cincinnati Childrens Hospital Medical Center
3333 Burnet Avenue
Cincinnati Ohio 45229
Kasabach-Merritt phenomenon Resources
George M, Singhal V, Sharma V, Nopper AJ. Successful surgical excision of a complex vascular lesion in an infant with Kasabach-Merritt syndrome. Pediatr Dermatol. 2002;19(4):340-4.
Haisley-Royster C, Enjolras O, Frieden IJ, et al. Kasabach-merritt phenomenon: a retrospective study of treatment with vincristine. J Pediatr Hematol Oncol. 2002;24(6):459-62.
Hesselmann S, Micke O, Marquardt T, et al. Case report: Kasabach-Merritt syndrome: a review of the therapeutic options and a case report of successful treatment with radiotherapy and interferon alpha. Br J Radiol. 2002;75(890):180-4.
Enjolras O, Wassef M, Mazoyer E, et al. Infants with Kasabach-Merritt syndrome do not have "true" hemangiomas. J Pediat. 1997;130(4):631-40.
Ezekowitz RA, Mulliken JB, Folkman J. Interferon alfa-2a therapy for life-threatening hemangiomas of infancy. N Engl J Med. 1992;326(22):1456-63.
Krafchik BR, Hendricks LK. Kasabach-Merritt Syndrome. Emedicine. http://emedicine.medscape.com/article/202455-overview. Updated February 22, 2010. Accessed April 5, 2012.
Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Hemangioma-Thrombocytopenia Syndrome. Entry No: 141000. Last Edited November 27, 2007. Available at: http://www.ncbi.nlm.nih.gov/omim/. Accessed April 5, 2012.
Vasquez M-P. Kasabach-Merritt syndrome; Orphanet. http://www.orpha.net//consor/cgi-bin/OC_Exp.php?Lng=GB&Expert=2330. Last Updated May 2006. Accessed April 5, 2012.
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