Myeloproliferative neoplasms

A heterogeneous group of proliferative disorders of the precursors of red and white blood cells and platelets in the bone marrow. It leads to abnormalities in the number, maturation or function of these cells, although depending on the type, one line or another will be affected to a greater extent. It has been estimated to have an overall annual incidence of 2.17 cases per 100,000 inhabitants and a variable evolution and prognosis.

The following types of myeloproliferative neoplasms have been described, chronic myelogenous leukemia, polycythemia vera, primary myelofibrosis (or idiopathic chronic myelofibrosis), essential thrombocythemia, chronic neutrophilic leukemia, and chronic eosinophilic leukemia.nic idiopathic myelofibrosis), essential thrombocythemia, chronic neutrophilic leukemia, and chronic eosinophilic leukemia.

The exact cause is unknown, but a number of factors are likely to be involved. Available studies have shown that there is usually a change in the genetic material of the bone marrow cells producing the growing precursors, acquired over time, with only very rare cases occurring in families.

Likewise, different factors have been described that contribute to the risk of these myeloproliferative neoplasms:

  • Age: it can occur at any age, but is frequently diagnosed after the age of 50.
  • Very high doses of ionizing radiation, chemotherapy or radiotherapy treatments for a previous malignant tumor.
  • Prolonged exposure to high levels of chemical compounds such as benzene (also present in minute amounts in cigarette smoke) or toluene.
  • Other myeloproliferative disorders: a small fraction of cases of myelofibrosis result from a complication of essential thrombocythemia or polycythemia vera.

Evidence from family and epidemiological studies has revealed a significant heritable component that implies a 5 to 7-fold increased risk in first-degree relatives, as well as contributing to the observed phenotypic variability. In this regard, large-scale GWAS analysis of nearly 4000 cases and nearly 1500000 controls has identified 12 risk loci related to other hematopoietic traits of different lineages and chromatin remodeling of these precursors, as well as increased leukocyte telomere length and other clonal hematopoietic states.

Symptoms

They are often symptomless and are detected accidentally during routine testing. Once symptoms occur there is great variability between individuals, and they progress gradually over time including:

  • Headache, dizziness, fever.
  • Blurred vision.
  • Fatigue, weakness.
  • Bruising, petechiae (red spots under the skin), frequent bleeding.
  • Unexplained weight loss.
  • Difficulty breathing.
  • Itching of the skin.
  • Night sweats
  • Increased blood pressure.

In addition, in all of them there are, to a greater or lesser degree, medullary fibrosis and splenomegaly and hyperuricemia as a consequence of proliferation. Generally the chronic course tends to evolve towards a global medullary failure or, more frequently, towards an acute leukemia.

Prevention

There are currently no guidelines available regarding the prevention of myeloproliferative neoplasms since the exact triggers are unknown. However, as for other conditions, it is advisable to follow a healthy lifestyle based on a balanced diet, regular physical exercise and avoidance of harmful habits such as smoking or excessive consumption of alcohol and other substances of abuse.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

12 loci

Bibliography

McMullin MF et al. Aetiology of Myeloproliferative Neoplasms. Cancers (Basel). 2020;12(7):1810.

Leukaemia Foundation [April 2022]

MD Anderson Center [April 2022]

WebMD Cancer Center [April 2022]

Bao EL et al. Inherited myeloproliferative neoplasm risk affects hematopoietic stem cells. Nature. 2020 Oct;586(7831):769-775.

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