What is KMP in medical terms? A Comprehensive Guide

September 23, 2025 •

4 min read

Affecting infants and young children, Kasabach-Merritt Phenomenon (KMP) is a rare and potentially life-threatening bleeding disorder that is associated with certain vascular tumors. Understanding what is KMP in medical terms is crucial for early detection and effective management of this complex condition. This phenomenon causes a severe drop in platelets and other clotting factors, posing a significant bleeding risk.

Quick Summary

KMP, or Kasabach-Merritt Phenomenon, is a rare bleeding disorder typically seen in infants with certain vascular tumors like kaposiform hemangioendothelioma (KHE) or tufted angioma (TA), leading to a dangerously low platelet count and other clotting abnormalities.

Key Points

Rare Bleeding Disorder: Kasabach-Merritt Phenomenon (KMP) is a life-threatening coagulopathy affecting infants with specific vascular tumors, not a common condition.
Caused by Vascular Tumors: KMP is triggered by either a kaposiform hemangioendothelioma (KHE) or a tufted angioma (TA).
Platelet Consumption: The core problem in KMP is that the tumor traps and destroys platelets and other clotting factors, leading to a severe and rapid drop in their numbers.
Risk of Bleeding: The resulting thrombocytopenia and coagulopathy put the patient at a high risk for spontaneous and life-threatening bleeding.
Complex Treatment: Management requires a team of specialists and often involves systemic medications like vincristine or sirolimus to shrink the tumor, addressing the root cause.
Diagnosis is Critical: Prompt and accurate diagnosis, often involving blood tests and imaging, is crucial for improving the patient's prognosis.

What is the Kasabach-Merritt Phenomenon (KMP)?

KMP is a consumptive coagulopathy, a condition where the body's clotting factors are used up at a rate that the body cannot replenish. This occurs when large, fast-growing vascular tumors trap and destroy platelets and other clotting factors. This process can lead to profound thrombocytopenia (low platelet count), hypofibrinogenemia (low fibrinogen), and anemia. It is a rare, but serious, complication primarily affecting infants and is associated specifically with two types of vascular tumors: kaposiform hemangioendothelioma (KHE) and tufted angioma (TA). The severity of KMP depends on the tumor's size, location, and aggressiveness.

The Underlying Mechanism of KMP

At the heart of KMP's pathology is the sequestration of platelets and clotting factors within the abnormal vasculature of the tumor. This process involves:

Intratumoral Platelet Trapping: The unique endothelial architecture of KHE and TA tumors creates a slow, turbulent blood flow environment. This promotes the trapping and activation of platelets within the tumor's blood vessels.
Platelet Destruction: The trapped platelets are consumed and destroyed within the tumor, leading to a systemic shortage of platelets. This results in the characteristic severe thrombocytopenia.
Coagulopathy: The process is further complicated by the consumption of coagulation factors, such as fibrinogen. The rapid utilization of these factors leads to a state of consumptive coagulopathy, where the body's ability to form clots is severely impaired.

Clinical Manifestations and Diagnosis

The signs and symptoms of KMP are closely linked to the underlying vascular tumor and the resulting coagulopathy. A rapid diagnosis is vital for a favorable outcome.

Common Clinical Signs

Rapidly Enlarging Tumor: The associated vascular tumor (KHE or TA) often grows quickly, becoming firm, purplish, and tender.
Bleeding and Bruising: Due to the low platelet count, infants may exhibit petechiae (tiny red or purple spots), widespread bruising (purpura), and prolonged bleeding from minor injuries or needle sticks.
Anemia: Significant blood loss trapped within the tumor can lead to a dangerously low red blood cell count.
Respiratory Distress: If the tumor is located in the chest or abdomen, it can compress vital organs, causing breathing difficulties or organ dysfunction.

Diagnostic Tools

Complete Blood Count (CBC): A key laboratory finding is profound thrombocytopenia (platelet count often below 60,000/µL).
Coagulation Studies: These tests reveal hypofibrinogenemia, elevated D-dimer levels, and possibly a prolonged prothrombin time (PT) or activated partial thromboplastin time (aPTT).
Imaging: MRI and ultrasound are used to visualize the size, location, and extent of the vascular tumor associated with KMP.
Biopsy: While the gold standard for diagnosis, a biopsy is often avoided in severe KMP cases due to the high bleeding risk.

Management and Treatment Strategies

Treatment for KMP is complex and multidisciplinary, requiring collaboration between hematologists, oncologists, surgeons, and interventional radiologists. The primary goal is to address the coagulopathy and shrink the vascular tumor.

Medical Therapies

Drug Therapy: Systemic medications are often the first line of treatment. Vincristine is a common agent used to slow tumor growth, while corticosteroids or sirolimus may also be used, sometimes in combination. Sirolimus, in particular, has emerged as a promising therapy.
Platelet Transfusions: While transfusions can temporarily help with bleeding, they are generally used cautiously as they can lead to further tumor enlargement by supplying more platelets to be trapped. They are typically reserved for active bleeding or before necessary procedures.

Procedural Interventions

Surgical Excision: For small, well-defined tumors, surgical removal may be an option. However, many KHE and TA tumors are diffuse and infiltrative, making complete removal difficult or impossible.
Embolization: An interventional radiologist may perform this procedure to block the main blood supply to the tumor, helping to shrink it.
Radiation Therapy: This is sometimes used for aggressive tumors that do not respond to other treatments, though it is typically a last resort due to potential long-term side effects.

KMP vs. Other Blood Disorders

To better understand the uniqueness of KMP, it's helpful to compare it with other, more common, platelet disorders.


Feature	Kasabach-Merritt Phenomenon (KMP)	Idiopathic Thrombocytopenic Purpura (ITP)	Disseminated Intravascular Coagulation (DIC)
Underlying Cause	A specific vascular tumor (KHE or TA) that traps platelets.	Autoimmune condition where the body produces antibodies that destroy platelets.	Widespread activation of clotting cascades throughout the body due to a severe underlying illness (e.g., sepsis, cancer).
Onset	Primarily in infancy or early childhood.	Can occur at any age.	Occurs secondary to another severe medical condition.
Platelet Count	Severely low due to consumption and destruction within the tumor.	Severely low due to antibody-mediated destruction.	Can be low due to widespread consumption, but may fluctuate.
Fibrinogen Levels	Typically low (hypofibrinogenemia) due to consumptive coagulopathy.	Usually normal.	Low due to widespread consumption.
Primary Treatment	Focus on shrinking the tumor, often with vincristine or sirolimus.	Steroids or IVIG to suppress the immune system. Splenectomy in severe, refractory cases.	Treat the underlying cause (e.g., antibiotics for sepsis) and support with blood products.

Prognosis and Long-term Outlook

The prognosis for KMP has improved significantly with advancements in diagnostic and treatment methods, but it remains a life-threatening condition. Early and accurate diagnosis, followed by prompt and aggressive medical management, is key to a positive outcome. With successful treatment, the vascular tumor typically regresses, and the hematological abnormalities resolve. However, the long-term outlook depends on factors such as the tumor's size, location, and responsiveness to therapy. Some children may experience lasting complications related to the tumor or its treatment. The rarity of the condition necessitates care at specialized vascular anomalies centers, where expert teams can provide comprehensive and tailored treatment plans. For more detailed information on Kaposiform Hemangioendothelioma and associated conditions, you can consult a specialized resource like Boston Children's Hospital.

Frequently Asked Questions

Primary symptoms of Kasabach-Merritt Phenomenon (KMP) include a rapidly enlarging vascular tumor that may be purplish or bruised-looking, petechiae (tiny spots), widespread bruising, and signs of internal bleeding like anemia or organ compression if the tumor is internal.

No, KMP is not the same as a typical infantile hemangioma. KMP is a specific, rare complication that is associated with more aggressive vascular tumors, such as KHE and TA. Common infantile hemangiomas do not typically cause KMP.

While KMP is a serious condition, it can often be successfully managed and resolved with prompt and appropriate treatment. The goal is to treat the underlying vascular tumor, which then leads to the resolution of the coagulopathy.

Platelet transfusions can exacerbate the problem in KMP because the transfused platelets can be consumed by the tumor, causing it to grow larger. They are typically reserved for controlling acute bleeding or during necessary procedures, not for routine management of the low platelet count.

KMP is a localized consumptive coagulopathy caused by a specific vascular tumor, while Disseminated Intravascular Coagulation (DIC) is a systemic consumptive coagulopathy triggered by a severe underlying illness, such as sepsis or trauma.

A kaposiform hemangioendothelioma (KHE) is a rare vascular tumor that often appears in infants and is one of the primary causes of KMP. It is an abnormal growth of blood vessels that traps and destroys platelets, leading to the coagulopathy.

The treatment for KMP requires a multidisciplinary team of specialists. This typically includes a hematologist/oncologist, a dermatologist, a vascular anomalies expert, and potentially an interventional radiologist or surgeon, depending on the case.