In myeloproliferative neoplasms (myelo = bone marrow; proliferative = rapid multiplication; and neoplasm = new abnormal growth, such as a precancer or cancer), the blood-producing cells in the bone marrow (precursor cells, also called stem cells) reproduce excessively or are crowded out by an overgrowth of fibrous tissue. Sometimes, blood-producing cells appear and reproduce in the spleen and liver.
Myeloproliferative neoplasms are caused by genetic mutations. Typically the mutations are acquired and not inherited, although rarely there are families in which several members have these disorders.
The myeloproliferative neoplasms include
A myeloproliferative neoplasm can progress or transform to acute leukemia.
Less common myeloproliferative neoplasms include hypereosinophilic syndromes and chronic neutrophilic leukemia. There are also rare myeloproliferative neoplasms that overlap with myelodysplastic syndrome, another type of condition with abnormal blood-forming cells in the bone marrow.
Each myeloproliferative neoplasm is identified according to its predominant bone marrow and blood characteristics. Each disorder has a somewhat typical set of examination findings, test results, and expected course; however, there may be some overlap of features among these disorders because they share the same genetic mutations.
The number of blood-producing cells in the bone marrow can also increase as a reaction to another underlying disorder. For example, lack of oxygen can cause the red blood cells to increase, a serious infection can cause the white blood cells to increase, and inflammation can cause the platelets to increase. In these cases, an increased number of cells in the bone marrow is not considered a myeloproliferative neoplasm but rather a benign reaction. Treating the underlying disorder restores the number of blood cells being produced to normal.
Major Myeloproliferative Neoplasms
Disorder | Bone Marrow Characteristics | Blood Characteristics |
|---|---|---|
Increased number of mature and immature white cells | Increased number of a certain type of white blood cell (granulocytes) Sometimes increased number of platelets | |
Increased number of cells that produce the circulating blood cells | Increased number of red blood cells Usually, increased number of platelets, white blood cells, or both | |
Excess fibrous tissue replacing blood-producing cells | Decreased number of red blood cells (anemia) and an increased number of white blood cells Misshapen red blood cells The numbers of white blood cells and platelets often eventually decrease, but in some people they increase | |
Increased number of cells that produce platelets (megakaryocytes) | Increased number of platelets |
