Kasabach-Merritt syndrome is a blood-clotting disorder with links to rare blood vessel disorders. It often occurs in younger people, and the possible complications of the syndrome can be life threatening.
Blood clots, also known as a thrombus, refer to the final product of the blood coagulation step in hemostasis. Blood clot formation is an important process that prevents excessive bleeding after blood vessel injury. When the process of forming blood clots does not work correctly, people may bruise or bleed easily.
Kasabach-Merritt syndrome, also known as Kasabach-Merritt phenomenon, refers to blood-clotting problems that occur due to a rare, noncancerous tumor of the blood vessels.
The condition can be a serious disease, but with an early diagnosis and prompt treatment, the outlook is often positive.
KMP occurs due to a rare, rapidly growing mass of blood vessels that may be present at birth or develop during infancy. These masses can either be a kaposiform hemangioendothelioma (KHE) or a tufted angioma (TA).
Both masses are a type of hemangioma, which are benign tumors that affect blood vessels. These masses then trap and activate components necessary for blood clots known as platelets. This results in thrombocytopenia, or a low platelet count. As such, some healthcare professionals may also refer to KMP as hemangiomas with thrombocytopenia.
KMP typically occurs when fast-growing vascular tumors trap and destroy platelets. This results in fewer platelets, which interferes with blood clotting and increases the risk of serious bleeding. KMP occurs most often during infancy and is more likely to occur in children under 6 months of age.
The blood vessel tumors that can cause KMP include KHE and TA.
KHE tumors can have the appearance of a birthmark and usually grow in the soft tissues of the head, neck, and limbs. They are benign but can lead to severe complications due to their location. KHEs have close links to KMP and only rarely develop without causing it.
TA tumors most often develop before 5 years of age. They may appear as a small bruise-like area that continues to grow and does not improve with time. Some cases of TA have an association with KMP.
The main symptoms of KMP relate to bleeding that occurs due to a lack of platelets. Having too few platelets circulating also means a child with KMP is prone to bruising and developing small bruises under the skin known as petechiae. A child may also have a notable vascular lesion present on their skin, which can present similar to a birthmark.
Other signs and symptoms may include:
- enlarged abdomen
- enlarged liver
- painful lesions
- anemia
Complications can occur depending on the location of the masses. For example, when they are present in the chest or abdomen, they may cause significant illness and can be life threatening due to bleeding.
A doctor may refer an infant for KMP testing if they notice skin lesions and the easy development of bruises or bleeding. They may request a range of blood and imaging tests depending on the health of the infant. These can include:
- a full blood panel
- a test to measure the clotting factors, including testing fibrin levels
- ultrasounds or MRI scans
- angiography
- biopsy
These can give doctors an idea of whether an infant’s blood has enough clotting agents, as well as the location, aggressiveness, and size of any tumors. The doctor can also use a biopsy — in which they collect tissue to send to a lab for examination under a microscope — to confirm a diagnosis.
A multidisciplinary medical team will work together to treat KMP. This may involve:
- doctors who specialize in treating childhood disease, or pediatricians
- doctors who specialize in treating skin disorders, or dermatologists
- doctors who specialize in treating blood disorders, or hematologists
- surgeons
- radiologists
If a child has only mild symptoms, they may not require active treatment. Instead, their healthcare team can regularly monitor them to ensure they identify any potential problems early. However, if they have more severe platelet and clotting problems, they will require treatment. This will typically focus on treating the underlying tumor to help resolve KMP symptoms.
Initial treatment for KMP usually involves a regimen of oral steroids or chemotherapy. These drugs can help to improve symptoms and slow the growth of the tumor. A doctor may also recommend embolization to block the blood vessels in the lesion, which may help to stop it growing and improve the platelet count.
In other cases, such as if the tumor is very small or extremely aggressive, a doctor may suggest surgery to completely remove the mass.
Kasabach-Merritt syndrome, also known as Kasabach-Merritt phenomenon, is a rare condition that impacts blood clotting. It occurs most often in children due to vascular tumors causing low platelet counts. It typically results from two types of masses: Kaposiform hemangioendothelioma or tufted angioma.
These blood vessel tumors trap and destroy platelets. This results in blood-clotting problems and increases the risk of bruising and serious bleeding. The condition can lead to life threatening bleeds if the tumors develop on an internal organ.
Treatment often involves medications, such as chemotherapy drugs, to treat the tumor. Other cases may involve embolization to stop the tumor growing or surgery to remove the tumor.