Myelodysplastic or Myeloproliferative Neoplasms (Leukemia Types)

Three main types of myelodysplastic syndromes/myeloproliferative neoplasms are as follows:

1. Chronic myelomonocytic leukemia (CMML)

It is rare cancer affecting the blood and bone marrow. It is characterized by the abnormal production of a type of white blood cell called monocytes and other abnormal cells in the blood.

It is more common in older adults, with the average age at diagnosis being about 70 years. The exact cause of CMML is not known, but it is thought to be related to genetic abnormalities that affect the average production and function of blood cells. There are no known ways to prevent CMML, and the condition is usually diagnosed through a combination of blood tests, bone marrow biopsy, and imaging tests.

CMML can progress to a more advanced form of leukemia called acute myeloid leukemia, and it may affect other organs, such as the liver and spleen. Symptoms of CMML may include fatigue, weakness, anemia, bruising or bleeding easily, and infections. Treatment options may include medications to control the production of abnormal cells, blood transfusions, and bone marrow transplantation.

Several genetic abnormalities have been associated with the development of CMML, such as:

• Somatic mutations: These are changes in the DNA of certain cells that occur after a person is born. Some of the most common somatic mutations in CMML include changes in the TP53, NRAS, and TET2 genes.
• Chromosomal translocations: These are changes in which pieces of chromosomes are swapped or rearranged. A common chromosomal translocation in CMML involves the RAS oncogene located on chromosome 3.
• Monosomy 7: This is a condition in which a person is missing one copy of chromosome 7. Monosomy 7 is found in about 50 percent of people with CMML.
• Tetrasomy 8: This is a condition in which a person has four copies of chromosome 8 instead of the normal two copies. Tetrasomy 8 is found in about 15 percent of people with CMML.

Not all people with CMML have these genetic abnormalities, and the specific genetic changes present can vary from person to person. Further research is required to understand the role of genetics in the development and progression of CMML.

2. Juvenile myelomonocytic leukemia (JMML)

It is rare cancer affecting the blood and bone marrow. JMML is mostly diagnosed in children younger than four years, and it is characterized by the abnormal production of certain types of blood cells, including monocytes.

JMML can affect other organs, such as the liver and spleen. Symptoms of JMML may include fever, fatigue, easy bruising or bleeding, and infections. JMML is a serious condition that requires prompt medical treatment. 

Treatment options may include chemotherapy, stem cell transplantation, and medications to control the production of abnormal cells. The prognosis for JMML varies widely, but early diagnosis and treatment can improve the chances of a successful outcome.

The exact cause of JMML is not fully understood yet. However, it is thought to be related to genetic abnormalities that affect the average production and function of blood cells. 

Several genetic abnormalities have been associated with the development of JMML. These genetic changes can be inherited or acquired during a person's lifetime and include the following:

• Mutations in the CBL gene: This gene is involved in regulating the production of white blood cells. Mutations in the CBL gene have been found in about 30 percent of people with JMML.
• Other genetic mutations: Mutations in genes that are involved in signaling pathways that control cell growth and division can cause JMML. These genes include the following:
  • NRAS gene: Mutations in this gene are seen in about 25 percent of people with JMML.
  • KRAS gene: These mutations have been found in about 20 percent of people with JMML.
  • PTPN11 gene: These mutations have been found in about 20 percent of people with JMML.

3. Atypical chronic myelogenous leukemia (aCML)

It is a rare subtype of chronic myelogenous leukemia (CML) that has features different from those of classic CML. aCML is less common than classic CML, and it is a slow-growing condition. However, aCML can still progress to a more advanced form of leukemia called blast crisis if left untreated. 

Symptoms of aCML may include fatigue, weakness, anemia, and infections. Treatment options may include medications (such as imatinib) to control the production of abnormal cells and bone marrow transplantation.

The exact cause of aCML is not fully understood. However, it is thought to be related to genetic abnormalities that affect the average production and function of blood cells. 

aCML is caused by a genetic abnormality called the Philadelphia chromosome, which results from a translocation between chromosomes 9 and 22. This translocation leads to the production of a fusion protein called BCR-ABL, which promotes the abnormal growth and division of white blood cells. Philadelphia chromosome may not be present in all people with aCML, and other genetic changes may be involved in the development of this subtype of leukemia.

Myelodysplastic syndrome (MDS), sometimes called myelodysplastic leukemia, is characterized by the production of abnormal blood cells in the bone marrow, which can lead to a decrease in healthy blood cells such as red blood cells, white blood cells, and platelets. 

Symptoms of MDS may include fatigue, shortness of breath, easy bruising or bleeding, and an increased risk of infections.

A variety of factors, including exposure to certain chemicals, radiation therapy, and certain medications can cause MDS. It can also occur because of a genetic mutation or as a complication of another medical condition.

Treatment for MDS may include medications to help the bone marrow produce normal blood cells, blood transfusions to increase the number of healthy blood cells in the body, and other supportive therapies. In advanced cases, a bone marrow transplant may be necessary.

Myeloproliferative neoplasms (MPNs) are a group of disorders that affect the production and function of blood cells. The overproduction of specific blood cells, such as red blood cells, white blood cells, or platelets characterizes MPN. This can lead to an increase in the number of these blood cells in the bloodstream, which can cause various symptoms, such as fatigue, bone pain, and an increased risk of blood clots.

The symptoms can vary depending on the type of MPN and the specific blood cells affected. 

Some common symptoms of MPN may include:

• Fatigue
• Bone pain
• Dizziness
• Headaches
• Shortness of breath
• Easy bruising or bleeding

Treatment for MPN may include medications to reduce the production of abnormal blood cells, blood transfusions to increase the number of healthy blood cells in the body, and other supportive therapies. A bone marrow transplant may be an option in the advanced stages.