KidsMD Health Topics


  • Overview

    If your child has been diagnosed with Kasabach-Merritt phenomenon (KMP), a complication in which certain vascular tumors trap and destroy platelets, we understand that you are very concerned about your child’s health. You probably have a lot of questions about this complex condition and the vascular tumors that cause it.

    Here’s what you need to know about Kasabach-Merritt phenomenon:

    • Kasabach-Merritt phenomenon is a serious complication because platelets help form blood clots to stop bleeding. If your child doesn’t have enough of them, your child may have an increased risk of bleeding.
    • Kasabach-Merritt phenomenon is never caused by common infantile hemangiomas.
    • It’s associated with the following tumors:
    • KMP is associated with larger, more aggressive or more deeply invading benign vascular tumors. As doctors shrink the tumor with medications, KMP goes away.
    • We treat the underlying tumor that’s associated with KMP, not the KMP itself. Please see details about treatments in the links above for your child’s specific tumor.

    How Children’s Hospital Boston approaches Kasabach-Merritt phenomenon
    Because Kasabach-Merritt phenomenon and the associated vascular tumors are so rare, we recommend that children with KMP be evaluated by an expert vascular anomalies center. In articles and on the web, KMP is confused with any blood test related to clotting or bleeding in a patient with a birthmark, hemangioma or vascular tumor. This is incorrect and leads to the wrong diagnosis and ineffective treatment plans in some cases.

    Here at Children’s Vascular Anomalies Center, we have the world’s largest database of children whose vascular tumors have caused Kasabach-Merritt phenomenon. When doctors anywhere in the world have questions about whether a child’s birthmark may be a vascular tumor that could lead to Kasabach-Merritt phenomenon, they often call us. Our physicians have treated more children with Kasabach-Merritt phenomenon than any other hospital in the world—which means that your child will get expert care from experienced physicians.

    The database

    Children’s Vascular Anomalies Center has the largest database in the world of children who have experienced Kasabach-Merritt phenomenon — currently more than 125 cases of vascular anomalies with KMP. As our database grows, it will help shine more light on this rare and often misunderstood condition.

    Kasabach-Merritt phenomenon: Reviewed by Cameron C. Trenor III, MD,
    © Children’s Hospital Boston, 2010

    Contact us text

  • In depth text

  • Tests

    The first step in treating your child is forming an accurate and complete diagnosis.

    Diagnosing Kasabach-Merritt phenomenon (KMP) can be difficult for many physicians simply because it’s such a rare condition. The specialists at the Vascular Anomalies Center at Children’s Hospital Boston understand how KMP works and so can easily identify it—and begin treatment to help your child get better.

    How do I know if my child has Kasabach-Merritt phenomenon?

    The only way to diagnose Kasabach-Merritt phenomenon is through a blood test.

    • Complete blood count (CBC) — If your child’s doctor suspects Kasabach-Merritt phenomenon, he or she will order a complete blood count to check your child’s platelet level. If it’s low, your child has Kasabach-Merritt phenomenon.
    • Often, other laboratory tests related to bleeding are also performed, including prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and D-dimer. These assess for other bleeding problems often confused with KMP and may be clues about alternative diagnoses.

    What are these tests like?

    One of the members of your care team (probably a nurse or phlebotomist) will take a little blood from your child and collect it in a small tube. Our lab then analyzes your child’s blood and sends the results to your doctor. If your child’s doctor diagnoses Kasabach-Merritt phenomenon, you’ll learn about your treatment options.

    When should I consult a vascular anomalies specialist?

    We advise consulting a vascular anomalies specialist in three situations:

    • if your child has a vascular skin lesion and a low platelet count
    • if your child has a vascular skin lesion that seems to be growing beyond expectations
    • if your child has a vascular skin lesion that gets larger, darker and more painful after a platelet transfusion

    After we complete all necessary tests, our experts meet to review and discuss what they have learned about your child's condition. Then we will meet with you and your family to discuss the results and outline the best treatment options.

    Your appointment

    Questions about your visit? Read about directions, contact information and other important information. 

  • Undoubtedly, you were distressed when you learned that your child is at risk of developing a bleeding disorder because of Kasabach-Merritt phenomenon. But at Boston Children's Hospital, we view the diagnosis as a starting point: Now we're able to begin the process of treating your child—shrinking the tumor and increasing the platelet count—so that we may ultimately return your child to good health.

    We treat the underlying vascular tumor, not the KMP itself. Please see the links below to your child's vascular tumor to see how we are currently approaching treatment decisions.

    Supportive care

    We want to maximize the safety and effectiveness of whatever therapy you and your child's doctor decide upon.

    • Supportive care involves preventing and treating infections and side effects of treatment to keep your child as comfortable as possible while we're working to shrink the tumor and increase your child's platelet count.

    Continual follow-up care

    A schedule of follow-up care will be determined by your child's physician and other members of your care team to see how your child is responding to the therapy and check for recurrence of the tumor, a drop in platelet count or a worsening of the lesion.

    And after we have succeeded in shrinking the tumor and treating the Kasabach-Merritt phenomenon, there may be some residual marks on your child's skin. Depending on where they are and how large they are, you may want to consider a cosmetic procedure, which can be done by one of our plastic surgeons.

    Coping and support

    We understand that you may have a lot of questions when your child is diagnosed with Kasabach-Merritt phenomenon. We hope that this site reassures you and begins to prepare you for the next steps in treating your child's underlying vascular tumor. There are also a number of other resources to help you and your family through this difficult time.

    Patient education: From the first office visit, our nurses will be on hand to walk you through your child's treatment and help answer any questions you may have —What symptoms might my child have? What do we do next? They will also reach out to you by phone, continuing the care and support you received while at Children's.

    Parent to parent: Want to talk with someone whose child has been treated for a vascular tumor associated with KMP? We may be able to put you in touch with other families who can share their experience.

    Faith-based support: If you are in need of spiritual support, we will help connect you with the Children's chaplaincy. Our program includes nearly a dozen clergy representing Episcopal, Jewish, Lutheran, Muslim, Roman Catholic, Unitarian and United Church of Christ traditions who will listen to you, pray with you and help you observe your own faith practices during your hospital experience.

    Social work and mental health professionals: Our social workers and mental health clinicians have helped many other families in your situation. We can offer counseling and assistance with issues such as coping with your child's diagnosis, stresses relating to coping with illness and dealing with financial difficulties.

    On our For Patients and Families site, you can read all you need to know about:

    • getting to Children's
    • navigating the hospital experience
    • resources that are available for your family

    Our Vascular Anomalies Center offers links to organizations that offer support and education for parents who have a child with a vascular anomaly.

    Integrative therapies

    Our patient-centered approach means that we want your child to not only get better, but also feel good along the way. Throughout the hospital, you¹ll find clinicians trained in therapies that can make your child feel more comfortable, learn to shift focus away from pain and enjoy some peaceful moments during what may be an anxious time. Read more about how acupuncture, guided meditation, guided imagery, massage, Reiki and therapeutic touch could help your child.

    Child Life specialists

    "Don't forget to tell them the rules," 7-year-old Lia DiFronzo says to Amber Soulvie, her Child Life specialist. Read more about how our Child Life help children like Lia feel comfortable in the hospital.

  • Research & Innovation

    Boston Children's Hospital is a world leader in opening new avenues of "translational research," bringing laboratory advances to the bedside and doctor's office as quickly as possible. When doctors in other states or other countries need help diagnosing or treating vascular anomalies like the ones that cause Kasabach-Merritt phenomenon, they often come to us. We have more experience helping more children with KMP than any other hospital in the world.

    And we’re constantly increasing our base of knowledge. Physicians and researchers at the VAC are actively reviewing our extensive database with more than 125 cases complicated by KMP. As our database grows, it will help shine more light on a widely misunderstood condition. More importantly, consolidating knowledge about treatment, side effects and outcomes in this database will help us treat your child more effectively.

    The VAC conducts research that may lead to the development of new, more effective therapies and perhaps ultimately result in ways to prevent these anomalies. Read more about our research.

    Clinical and Translational Study Unit
     Read about a day in the life of the Clinical and Translational Study Unit at Children’s.
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The future of pediatrics will be forged by thinking differently, breaking paradigms and joining together in a shared vision of tackling the toughest challenges before us.”
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