Kasabach-Merritt syndrome
Encyclopedia
Kasabach–Merritt syndrome (KMS), also known as Hemangioma with thrombocytopenia) is a rare disease
, usually of infant
s, in which a vascular tumor
leads to decreased platelet
counts and sometimes other bleeding problems, which can be life-threatening. It is also known as hemangioma thrombocytopenia syndrome. It carries the names of Dr Haig Haigouni Kasabach and Dr Katharine Krom Merritt, the two pediatricians who first described the condition in 1940.
or other vascular tumor
, often present at birth. Although these tumors are relatively common, it is rare for them to cause KMS.
When these tumors are large or are growing rapidly, sometimes they can trap platelet
s, causing severe thrombocytopenia
. The combination of vascular tumor and consumptive thrombocytopenia defines KMS. Tumors can be found in the trunk, upper and lower extremities, retroperitoneum, and in the cervical and facial areas.
This consumptive coagulopathy also uses up clotting factors, such as fibrinogen
which may worsen bleeding. The coagulopathy can progress to disseminated intravascular coagulation
and even death.
Patients uniformly show severe thrombocytopenia, low fibrinogen
levels, high fibrin degradation products (due to fibrinolysis
), and microangiopathic hemolysis
.
s to guide therapy.
. The thrombocytopenia and coagulopathy are managed with platelet transfusions and fresh frozen plasma
, although caution is needed due to the risk of fluid overload and heart failure from multiple transfusions. The possibility of disseminated intravascular coagulation
, a dangerous and difficult-to-manage condition, is concerning. Anticoagulant
and antiplatelet medications can be used after careful assessment of the risks and benefits.
is feasible, it provides a good opportunity for cure (although it can be dangerous to operate on a vascular tumor in a patient prone to bleeding, even with appropriate surgical subspecialists involved).
If surgery is not possible, various other techniques can be used to control the tumor:
Furthermore, patients may need care from a dermatologist or plastic surgeon for residual cosmetic lesions. On long-term followup, most patients have skin discoloration and/or mild disfiguration from the dormant tumor.
Rare disease
A rare disease, also referred to as an orphan disease, is any disease that affects a small percentage of the population.Most rare diseases are genetic, and thus are present throughout the person's entire life, even if symptoms do not immediately appear...
, usually of infant
Infant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
s, in which a vascular tumor
Vascular tumor
Vascular tumor may mean:* tumor of vascular origin, a growth formed from blood vessels; for example, hemangioma, Lymphangioma, hemangioendothelioma, Kaposi sarcoma, angiosarcoma, etc....
leads to decreased platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
counts and sometimes other bleeding problems, which can be life-threatening. It is also known as hemangioma thrombocytopenia syndrome. It carries the names of Dr Haig Haigouni Kasabach and Dr Katharine Krom Merritt, the two pediatricians who first described the condition in 1940.
Pathophysiology
KMS is usually caused by a hemangioendotheliomaHemangioendothelioma
Hemangioendothelioma is used to describe a group of vascular neoplasms that may be considered benign or malignant in their activity.-Presentation:They have been described as masses that fall between a hemangioma and angiosarcoma...
or other vascular tumor
Vascular tumor
Vascular tumor may mean:* tumor of vascular origin, a growth formed from blood vessels; for example, hemangioma, Lymphangioma, hemangioendothelioma, Kaposi sarcoma, angiosarcoma, etc....
, often present at birth. Although these tumors are relatively common, it is rare for them to cause KMS.
When these tumors are large or are growing rapidly, sometimes they can trap platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
s, causing severe thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...
. The combination of vascular tumor and consumptive thrombocytopenia defines KMS. Tumors can be found in the trunk, upper and lower extremities, retroperitoneum, and in the cervical and facial areas.
This consumptive coagulopathy also uses up clotting factors, such as fibrinogen
Fibrinogen
Fibrinogen is a soluble plasma glycoprotein, synthesised by the liver, that is converted by thrombin into fibrin during blood coagulation. This is achieved through processes in the coagulation cascade that activate the zymogen prothrombin to the serine protease thrombin, which is responsible for...
which may worsen bleeding. The coagulopathy can progress to disseminated intravascular coagulation
Disseminated intravascular coagulation
Disseminated intravascular coagulation , also known as disseminated intravascular coagulopathy or consumptive coagulopathy, is a pathological activation of coagulation mechanisms that happens in response to a variety of diseases. DIC leads to the formation of small blood clots inside the blood...
and even death.
Diagnostic workup
The diagnostic workup is directed by the presenting signs and symptoms, and can involve:- blood counts, clotting studies, and other laboratory testing
- imaging tests (ultrasoundMedical ultrasonographyDiagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
, CT scan, MRI, sometimes angiography, and rarely nuclear medicineNuclear medicineIn nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
scans) - biopsyBiopsyA biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
of the tumor.
Patients uniformly show severe thrombocytopenia, low fibrinogen
Fibrinogen
Fibrinogen is a soluble plasma glycoprotein, synthesised by the liver, that is converted by thrombin into fibrin during blood coagulation. This is achieved through processes in the coagulation cascade that activate the zymogen prothrombin to the serine protease thrombin, which is responsible for...
levels, high fibrin degradation products (due to fibrinolysis
Fibrinolysis
Fibrinolysis is a process that prevents blood clots from growing and becoming problematic. This process has two types: primary fibrinolysis and secondary fibrinolysis...
), and microangiopathic hemolysis
Microangiopathic hemolytic anemia
In medicine microangiopathic hemolytic anemia is a microangiopathic subgroup of hemolytic anemia caused by factors in the small blood vessels. It is identified by the finding of anemia and schistocytes on microscopy of the blood film.-Presentation:It is referred as Runner's anemia...
.
Management
Management of KMS, particularly in severe cases, can be complex and require the joint effort of multiple subspecialists. This is a rare disease with no consensus treatment guidelines or large randomized controlled trialRandomized controlled trial
A randomized controlled trial is a type of scientific experiment - a form of clinical trial - most commonly used in testing the safety and efficacy or effectiveness of healthcare services or health technologies A randomized controlled trial (RCT) is a type of scientific experiment - a form of...
s to guide therapy.
Supportive care
Patient with KMS can be extremely ill and may need intensive care. They are at risk of bleeding complications including intracranial hemorrhageIntracranial hemorrhage
An intracranial hemorrhage is a hemorrhage, or bleeding, within the skull.-Causes:Intracranial bleeding occurs when a blood vessel within the skull is ruptured or leaks. It can result from physical trauma or nontraumatic causes such as a ruptured aneurysm...
. The thrombocytopenia and coagulopathy are managed with platelet transfusions and fresh frozen plasma
Fresh frozen plasma
The term fresh frozen plasma refers to the liquid portion of human blood that has been frozen and preserved after a blood donation and will be used for blood transfusion...
, although caution is needed due to the risk of fluid overload and heart failure from multiple transfusions. The possibility of disseminated intravascular coagulation
Disseminated intravascular coagulation
Disseminated intravascular coagulation , also known as disseminated intravascular coagulopathy or consumptive coagulopathy, is a pathological activation of coagulation mechanisms that happens in response to a variety of diseases. DIC leads to the formation of small blood clots inside the blood...
, a dangerous and difficult-to-manage condition, is concerning. Anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...
and antiplatelet medications can be used after careful assessment of the risks and benefits.
Definitive treatment
Generally, treatment of the underlying vascular tumor results in resolution of KMS. If complete surgical resectionSegmental resection
Segmental resection is a surgical procedure to remove part of an organ or gland. It may also be used to remove a tumor and normal tissue around it. In lung cancer surgery, segmental resection refers to removing a section of a lobe of the lung.- External links :* entry in the public domain NCI...
is feasible, it provides a good opportunity for cure (although it can be dangerous to operate on a vascular tumor in a patient prone to bleeding, even with appropriate surgical subspecialists involved).
If surgery is not possible, various other techniques can be used to control the tumor:
- embolizationEmbolizationEmbolization is a non-surgical, minimally-invasive procedure performed by an interventional radiologist and interventional neuroradiologists. It involves the selective occlusion of blood vessels by purposely introducing emboli.-Therapeutic applications:...
(by interventional radiologyInterventional radiologyInterventional radiology is a specialty of radiology, in which image-guided procedures are used to diagnose and treat a multitude of diseases across all body systems...
) can limit the tumor's blood supply - external compression bandages can have similar effects
- certain medications, including:
- corticosteroidCorticosteroidCorticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
s - alpha-interferon
- chemotherapyChemotherapyChemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
(e.g. vincristineVincristineVincristine , formally known as leurocristine, sometimes abbreviated "VCR", is a vinca alkaloid from the Catharanthus roseus , formerly Vinca rosea and hence its name. It is a mitotic inhibitor, and is used in cancer chemotherapy.-Mechanism:Tubulin is a structural protein that polymerizes to...
)
- corticosteroid
- radiation therapyRadiation therapyRadiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...
has been used, often successfully, but now is avoided whenever possible due to the risk of long-term adverse effects (e.g. risk for future cancer).
Outcomes
KMS has a mortality rate of about 30%. For patients that survive the acute disease, supportive care may be required through a gradual recovery.Furthermore, patients may need care from a dermatologist or plastic surgeon for residual cosmetic lesions. On long-term followup, most patients have skin discoloration and/or mild disfiguration from the dormant tumor.