Myelodysplastic/myeloproliferative diseases are a group of diseases in which the bone marrow makes too many white blood cells.

Myelodysplastic / myeloproliferative diseases are diseases of the blood and bone marrow. Normally, the bone marrow makes blood stem cells (immature cells ) that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. The lymphoid stem cell develops into a white blood cell. The myeloid stem cell develops into one of three types of mature blood cells:

• Red blood cells that carry oxygen and other materials to all tissues of the body.
• White blood cells that fight infection and disease.
• Platelets that help prevent bleeding by causing blood clots to form.

Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.

Myelodysplastic/myeloproliferative diseases have features of both myelodysplastic syndromes and myeloproliferative disorders.

In myelodysplastic diseases, the blood stem cells do not mature into healthy red blood cells, white blood cells, or platelets. The immature blood cells, called blasts, do not work the way they should and die in the bone marrow or soon after they enter the blood. As a result, there are fewer healthy red blood cells, white blood cells, and platelets.

In myeloproliferative diseases, a greater than normal number of blood stem cells develop into one or more types of blood cells and the total number of blood cells slowly increases.

This summary is about diseases that have features of both myelodysplastic and myeloproliferative diseases. See the following PDQ summaries for more information about related diseases:

• Myelodysplastic Syndromes Treatment
• Chronic Myeloproliferative Disorders Treatment
• Chronic Myelogenous Leukemia Treatment

There are different types of myelodysplastic/myeloproliferative diseases.

The 3 main types of myelodysplastic/myeloproliferative disease include the following:

• Chronic myelomonocytic leukemia (CMML).
• Juvenile myelomonocytic leukemia (JMML).
• Atypical chronic myelogenous leukemia (aCML).

When a myelodysplastic/myeloproliferative disease does not match any of these types, it is called myelodysplastic/myeloproliferative disease, unclassifiable (MDS/MPD-UC).

Myelodysplastic/myeloproliferative diseases may progress to acute leukemia.

Tests that examine the blood and bone marrow are used to detect (find) and diagnose myelodysplastic/myeloproliferative diseases.

The following tests and procedures may be used:

• Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease such as an enlarged spleen and liver. A history of the patient’s health habits and past illnesses and treatments will also be taken.
• Complete blood count (CBC) with differential: A procedure in which a sample of blood is drawn and checked for the following:
  • The number of red blood cells and platelets.
  • The number and type of white blood cells.
  • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
  • The portion of the sample made up of red blood cells.
  Complete blood count (CBC). Blood is collected by inserting a needle into a vein and allowing the blood to flow into a tube. The blood sample is sent to the laboratory and the red blood cells, white blood cells, and platelets are counted. The CBC is used to test for, diagnose, and monitor many different conditions.
• Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that produces it.
• Peripheral blood smear: A procedure in which a sample of blood is checked for the presence of blast cells, number and kinds of white blood cells, the number of platelets, and changes in the shape of blood cells.
• Cytogenetic analysis: A test in which cells in a sample of blood or bone marrow are viewed under a microscope to look for certain changes in the chromosomes. The cancer cells in myelodysplastic/myeloproliferative diseases do not contain the Philadelphia chromosome that is present in chronic myelogenous leukemia.
• Bone marrow aspiration and biopsy: The removal of a small piece of bone and bone marrow by inserting a needle into the hipbone or breastbone. A pathologist views both the bone and bone marrow samples under a microscope to look for abnormal cells. Bone marrow aspiration and biopsy. After a small area of skin is numbed, a Jamshidi needle (a long, hollow needle) is inserted into the patient’s hip bone. Samples of blood, bone, and bone marrow are removed for examination under a microscope.