Kasabach-Merritt phenomenon

What it is

From: Orphanet

A rare hemorrhagic disorder characterized by potentially life-threatening thrombocytopenia, microangiopathic hemolytic anemia, and consumptive coagulopathy in the context of kaposiform hemangioendothelioma or tufted angioma.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Hemangioma · Very frequent (99-80%)

A hemangioma is a benign tumor characterized by blood-filled spaces lined by benign endothelial cells. A hemangioma characterized by large endothelial spaces (caverns) is called a cavernous hemangioma (in contrast to a hemangioma with small endothelial spaces, which is called capillary hemangioma).

Hypofibrinogenemia · Very frequent (99-80%)

Decreased concentration of fibrinogen in the blood.

Thrombocytopenia · Very frequent (99-80%)

A reduction in the number of circulating thrombocytes.

Capillary hemangioma · Frequent (79-30%)

The presence of a capillary hemangioma, which are hemangiomas with small endothelial spaces.

Petechiae · Frequent (79-30%)

Petechiae are pinpoint-sized reddish/purple spots, resembling a rash, that appear just under the skin or a mucous membrane when capillaries have ruptured and some superficial bleeding into the skin has happened. This term refers to an abnormally increased susceptibility to developing petechiae.

Purpura · Frequent (79-30%)

Purpura (from Latin: purpura, meaning purple) is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin. This term refers to an abnormally increased susceptibility to developing purpura. Purpura are larger than petechiae.

Tufted angioma · Frequent (79-30%)

A vascular tumor of the skin and subcutaneous tissues and characterized by slow angiomatous proliferation.

Abnormal lymphatic vessel morphology · Occasional (29-5%)

A structural anomaly of the vessel that contains or conveys lymph fluid.

Anemia · Occasional (29-5%)

A reduction in erythrocytes volume or hemoglobin concentration.

Chronic disseminated intravascular coagulation · Occasional (29-5%)

A chronic form of disseminated intravascular coagulation in which a persistent weak or intermittent activating stimulus is present and destruction and production of coagulation factors and platelets are balanced.

Decreased total neutrophil count · Occasional (29-5%)

Abnormal decrease of absolute number of neutrophils in the blood, per microlitre, compared to a reference range for a given sex and age-group.

Hepatic hemangioma · Occasional (29-5%)

A congenital vascular malformation in the liver composed of masses of blood vessels that are atypical or irregular in arrangement and size.

Hyperhidrosis · Occasional (29-5%)

Abnormal excessive perspiration (sweating) despite the lack of appropriate stimuli like hot and humid weather.

Leukopenia · Occasional (29-5%)

An abnormal decreased number of leukocytes in the blood.

Other findings in the same source

From: Orphanet

Additional reported features include Prolonged prothrombin time (Occasional (29-5%)); Microangiopathic hemolytic anemia (Occasional (29-5%)); Abdominal distention (Very rare (<4-1%)); Abdominal pain (Very rare (<4-1%)); Hypertrichosis (Very rare (<4-1%)); Hypopnea (Very rare (<4-1%)); Neoplasm of the skin (Very rare (<4-1%)); Respiratory distress (Very rare (<4-1%)); Reticulocytosis (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Infancy; Neonatal

Inheritance in the source

From: Orphanet

Not applicable

Frequency and the population described

From: Orphanet

Reported case(s): 300.0; Worldwide. This is a published case count, not prevalence. Point prevalence: Unknown; Worldwide; Class only.

Which doctor should you see?

The suggested department for discussing Kasabach-Merritt phenomenon is Haematology, with a haematologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which blood-cell, marrow, bleeding or clotting finding matters most?
• Does the diagnosis need confirmation or a more precise subtype?
• Which symptoms or laboratory changes should trigger earlier review?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Kasabach-Merritt phenomenon. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.