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Definition of Myelofibrosis
Researchers do not know what causes myelofibrosis, which typically develops in people between the ages of 50 and 70, but believe it is an autoimmune response from a single defective blood stem cell (called a clonal dysfunction).
The immune system fails to recognize the deformed cells and produces antibodies to attack them.
The body’s efforts to repair this damage result in pervasive scar formation that progressively shuts down the bone marrow.
The most apparent consequence is severe anemia, as 99 percent of the bone marrow’s production is oxygen-bearing erythrocytes (red blood cells). The shortfall activates the body’s reserve erythropoietic functions in the liver and the spleen, which begin producing erythrocytes. However, these organs cannot meet the demand and so both begin to enlarge with the effort (hepatomegalyand splenomegaly, respectively).
Symptoms of myelofibrosis include those of anemia as well as bone pain, easy bleeding, and low resistance to infection as a consequence of diminished leukocyte (white blood cell) production. Blood tests show a low erythrocyte count, often low leukocyte and platelet counts, and characteristic “tear drop” deformity of the erythrocytes. Bone marrow biopsy shows the infiltration of fibrous tissue.
Treatment targets boosting the blood’s erythrocytes by blood transfusion and erythropoietin (epo) supplementation to stimulate the remaining red bone marrow to increase its erythrocyte production (erythropoiesis). Occasionally chemotherapy and radiation therapy to suppress bone marrow function, curtailing proliferation of the defective stem cells, slows the condition’s progression.
Bone marrow transplantation is sometimes a viable option. The outlook for myelofibrosis is variable; treatment is not curative and ultimately the bone marrow fails completely. Occasionally myelofibrosis evolves into acute myeloid leukemia, a rapidly progressive type of cancer in which blast cells (immature leukocytes) take over the bone marrow.