Kasabach-Merritt Syndrome: Causes and Treatments

Kasabach-Merritt Syndrome (KMS) is a rare and complex medical condition characterized by the presence of a vascular tumour, typically a hemangioma, which leads to a severe blood clotting disorder known as consumptive coagulopathy. This article aims to provide a detailed understanding of the syndrome, its causes, symptoms, diagnosis, treatment options, and risk factors and to elucidate the mechanisms of blood clotting involved in the condition.

Causes of Kasabach-Merritt Syndrome

Kasabach-Merritt Syndrome is primarily associated with the presence of certain vascular tumours. Unlike common hemangiomas, which are benign and typically resolve on their own, the tumours linked to KMS are more aggressive and can cause significant complications. The two main types of vascular tumours associated with KMS are:

Kaposiform Hemangioendothelioma (KHE): A rare vascular tumour that is locally aggressive and often associated with KMS.
Tufted Angioma: Another rare vascular lesion that can lead to KMS, though less commonly than KHE.

The exact pathophysiological mechanism by which these tumours lead to Kasabach-Merritt Syndrome is not entirely understood. However, it is believed that the cancer causes platelet trapping and activation, leading to a cycle of clotting and bleeding, which depletes clotting factors and results in consumptive coagulopathy.

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Symptoms of Kasabach-Merritt Syndrome

The symptoms of KMS can vary depending on the size and location of the vascular tumour. Commonly observed symptoms include:

Large Hemangiomas: These are often visible on the skin and can be firm, purple, and rapidly growing.
Bleeding and Bruising: Due to the consumptive coagulopathy, patients may experience unusual bleeding and bruising.
Anaemia: Resulting from blood loss and the destruction of red blood cells.
Thrombocytopenia: A marked decrease in platelet count due to platelet sequestration within the tumour.
Pain and Swelling: Caused by the growth of the tumour and associated inflammation.

Given the potential for severe bleeding and other complications, early recognition of these symptoms is crucial.

Diagnosis of Kasabach-Merritt Syndrome

The diagnosis of Kasabach-Merritt Syndrome is primarily clinical, supported by laboratory and imaging studies. The following steps are typically involved:

Clinical Evaluation: Initial assessment involves a thorough physical examination of the patient, focusing on the characteristics of the vascular lesion.
Blood Tests: Laboratory tests reveal thrombocytopenia, anaemia, and evidence of consumptive coagulopathy, such as decreased fibrinogen levels and elevated D-dimer.
Imaging Studies: Ultrasound, MRI, or CT scans are used to evaluate the extent of the vascular tumour and its effects on surrounding tissues.
Biopsy:In some cases, a biopsy may be required to confirm the diagnosis and rule out other conditions.

Treatment Options for Kasabach-Merritt Syndrome

Treating Kasabach-Merritt Syndrome is challenging and requires a multidisciplinary approach. The main goals of treatment are to manage the coagulopathy and reduce or eliminate the vascular tumour. Treatment options include:

Medical Management

Steroids: Corticosteroids are often the first line of treatment and can help reduce tumour size and improve blood clotting parameters.
Vincristine: An anti-cancer drug that has shown efficacy in shrinking KHE and tufted angiomas.
Interferon-alpha: Used in some cases to inhibit tumour growth, though it has notable side effects.
Sirolimus: An mTOR inhibitor that has gained popularity as a treatment for KMS due to its effectiveness and relatively lower side effect profile.

Surgical and Interventional Approaches

Surgery: In some cases, surgical removal of the tumour may be possible, though it is often challenging due to the risk of bleeding.
Embolization: A minimally invasive procedure that involves blocking the blood supply to the tumour, leading to its regression.

Supportive Care

Transfusions: Blood and platelet transfusions are sometimes necessary to manage anaemia and thrombocytopenia.
Monitoring and Management of Complications: Regular monitoring and prompt management of bleeding episodes and other complications are essential aspects of supportive care.

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Risk Factors for Kasabach-Merritt Syndrome

The precise risk factors for developing Kasabach-Merritt Syndrome are not well established due to its rarity. However, certain conditions and factors may increase the likelihood of developing the syndrome:

Presence of KHE or Tufted Angioma: The most significant risk factor is having one of these aggressive vascular tumours.
Infancy: KMS primarily occurs in infants and young children, although it can rarely be seen in adults.
Genetic Factors: While there is no clear genetic link, familial occurrences suggest a potential genetic predisposition.

Blood Clotting in Kasabach-Merritt Syndrome

The consumptive coagulopathy in KMS is a result of the abnormal blood clotting process instigated by the vascular tumour. The tumour acts as a site for platelet aggregation and clotting factor consumption, leading to:

Thrombocytopenia: Due to platelet sequestration within the tumour.
Hypofibrinogenemia: Caused by excessive consumption of fibrinogen.
Elevated Fibrin Degradation Products (D-dimer): Indicating ongoing coagulation and fibrinolysis.

This complex interplay results in a paradoxical situation where the patient is at risk for both bleeding and thrombosis, necessitating careful management and monitoring.

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