Kasabach-Merritt phenomenon

National Organization for Rare Disorders, Inc.

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  • KMP
  • thrombocytopenia with a vascular lesion
  • Kasabach-Merritt syndrome

Disorder Subdivisions

  • None

General Discussion

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.

Affected Populations

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.

Standard Therapies


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.

Investigational Therapies

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:

Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:


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





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.


NIH/National Heart, Lung and Blood Institute

P.O. Box 30105

Bethesda, MD 20892-0105

Tel: (301)592-8573

Fax: (301)251-1223

Email: nhlbiinfo@rover.nhlbi.nih.gov

Internet: http://www.nhlbi.nih.gov/

Hemangioma Support System

c/o Cynthia Schumerth

1484 Sand Acres Drive

DePere, WI 54115

Tel: (920)336-9399

Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/

Madisons Foundation

PO Box 241956

Los Angeles, CA 90024

Tel: (310)264-0826

Fax: (310)264-4766

Email: getinfo@madisonsfoundation.org

Internet: http://www.madisonsfoundation.org

National Organization of Vascular Anomalies

PO Box 38216

Greensboro, NC 27438-8216

Email: admin@mail.novanews.org

Internet: http://www.novanews.org

Venous Disease Coalition

1075 S. Yukon Street, Suite 320

Suite 320

Lakewood, CO 80226

Tel: (303)989-0500

Fax: (303)989-0200

Tel: (888)833-4463

Email: info@venousdiseasecoalition.org

Internet: http://www.venousdiseasecoalition.org

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.