What are myeloproliferative disorders?

What are myeloproliferative disorders?

Myeloproliferative disorders are diseases in which too many of certain types of blood cells are made in the bone marrow. The bone marrow is the spongy tissue inside the large bones in the body. The bone marrow makes red blood cells (which carry oxygen to all the tissues in the body), white blood cells (which fight infection), and platelets (which make the blood clot).

There are six types of myeloproliferative disorders: chronic myelogenous leukemia, polycythemia vera, chronic idiopathic myelofibrosis, essential thrombocythemia, chronic neutrophilic leukemia, and chronic eosinophilic leukemia. Chronic myelogenous leukemia affects the cells that are developing into white blood cells, called granulocytes. (Refer to the PDQ summary on Chronic Myelogenous Leukemia Treatment for more information.)

Polycythemia vera means too many red blood cells are made in the bone marrow and build up in the blood. The spleen (the organ in the upper abdomen that filters the blood to remove old cells) may swell because the extra blood cells collect there. Also, a person may have itching all over the body.

Chronic idiopathic myelofibrosis means red blood cells and certain white blood cells called granulocytes do not mature properly. The red blood cells look like teardrops instead of discs. The spleen may swell and there may be too few mature red blood cells to carry oxygen, causing anemia.

Essential thrombocythemia means the number of platelets in the blood is much higher than normal without any known cause, but other cells in the blood are normal. The extra platelets make it hard for the blood to flow normally.

Chronic neutrophilic leukemia means the number of the principal phagocyte (microbe-eating) cells that combat infection in the blood is much higher than normal without any known cause. The spleen and liver may swell.

Chronic eosinophilic leukemia means the number of white blood cells that participate in allergic reactions and help to fight certain parasitic infections is much higher than normal without any known cause.

If there are symptoms, a doctor will order blood tests to count the numbers of each of the different cells in the blood. If the results of the tests are not normal, more blood tests may be done. The doctor may also do a bone marrow biopsy. During this test, a needle is inserted into a bone to take out some of the marrow. The marrow is then looked at under a microscope. The doctor can then tell what kind of disease the patient has and plan the best treatment.

The chance of recovery (prognosis) depends on the type of myeloproliferative disorder, and the patient’s age and general health. The diseases usually vary from person to person, often progressing slowly and requiring little treatment. In some people, the disease may turn into an acute leukemia, in which too many white blood cells are made.

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