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Condition report · Hematological

MPL-Related Hereditary Thrombocythaemia

Whole genome sequencing reads the MPL gene for inherited changes that make the body produce too many platelets, which can raise the risk of blood clots and, less often, bleeding.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

An inherited condition in which the body makes too many platelets, which can raise the risk of blood clots or, less often, bleeding. It is caused by a change in one copy of the MPL gene, the receptor for the platelet-making hormone thrombopoietin.

Hereditary thrombocythaemia is an inherited condition in which the bone marrow makes too many platelets, the blood cells that help blood to clot. Raised platelet counts are often found on a routine blood test. Some people have clots, headaches or other circulation symptoms, and an enlarged spleen can occur. Less often there is bleeding, or scarring of the bone marrow.

It is caused by a change in one copy of the MPL gene, which makes the receptor for thrombopoietin, the hormone that drives platelet production. The inherited change makes this receptor overactive. Acquired changes in JAK2, CALR or MPL are more often the cause of raised platelet counts than inherited changes.

Follow-up with a haematologist monitors blood counts and clot risk. The report notes that low-dose aspirin is advised for patients, and that cytoreductive medicines are used for higher-risk disease. Genetic counselling is recommended, since relatives can have a blood count and testing.

The condition we analyse

Thrombocythaemia 2

Autosomal dominant

Thrombocythaemia 2 is caused by an inherited change in one copy of MPL that makes the thrombopoietin receptor overactive, so the bone marrow makes too many platelets.

Signs and symptoms

Raised platelet counts are often found on a routine blood test. Some people have blood clots, headaches or other symptoms related to circulation, and an enlarged spleen can occur. Less often there is bleeding or scarring of the bone marrow.

What a diagnosis changes

Follow-up with a haematologist is recommended to monitor blood counts and assess clot risk. Low-dose aspirin is advised for patients, and cytoreductive medicines are used for higher-risk disease. Genetic counselling is recommended; each child of an affected person has a 1 in 2 chance of inheriting the change, and relatives can have a blood count and testing.

Genes analysed

Also known as

familial thrombocytosis caused by mutation in MPL; MPL familial thrombocytosis; MPL-related thrombocythemia; THCYT2

MONDO:0011173OMIM 601977MedGen 477629Sources: [3][1][4]

Why whole genome sequencing

Raised platelet counts are more often caused by acquired changes than by inherited ones, so a negative result does not rule out thrombocythaemia. Whole genome sequencing reads MPL to look for an inherited cause.

Each child has a 1 in 2 chance

This condition is autosomal dominant, so each child of an affected person has a 50% chance of inheriting the change. Relatives can have a blood count and genetic testing, as the report recommends.

Clot risk guides follow-up

Follow-up with a haematologist is recommended to monitor blood counts and assess clot risk. Cytoreductive medicines are used for higher-risk disease, according to the report.

Limitations

  • Raised platelet counts are more often caused by acquired changes in JAK2, CALR or MPL than by inherited changes. A negative result does not rule out thrombocythaemia.

References

  1. MPL gene. MedlinePlus Genetics
  2. Essential thrombocythemia. MedlinePlus Genetics
  3. Guglielmelli P, Calabresi L, 2022. The MPL mutation. International review of cell and molecular biology
  4. Tefferi A, Vannucchi AM, Barbui T, 2024. Essential thrombocythemia: 2024 update on diagnosis, risk stratification, and management. American journal of hematology

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