Myelofibrosis

[Luis Fok]

Myelofibrosis is a disorder in which fibrous tissue in the bone marrow replaces the blood-producing cells, resulting in abnormally shaped red blood cells, anemia, and an enlarged spleen.

Myelofibrosis may occur on its own because of certain gene mutations, or it may occur as a result of other blood disorders.
People may feel tired and weak, have infections, and bleed easily.
Blood tests and a bone marrow biopsy are done for diagnosis.
Drugs and other treatments lessen the severity of anemia, increase red blood cell production, and fight infections.
Sometimes stem cell transplantation is used.

(See also Overview of Myeloproliferative Neoplasms.)
In normal bone marrow, cells called fibroblasts produce the fibrous (connective) tissue that supports the blood-producing cells. In myelofibrosis, the fibroblasts make too much fibrous tissue, which crowds out the blood-producing cells. When this occurs, some blood-producing cells migrate from the bone marrow to the spleen and liver. Overall, red blood cell production decreases, and anemia develops, becoming progressively more severe.
In addition, many of these red blood cells are immature or misshapen. Variable numbers of immature white blood cells and platelets also may be present in the blood. As myelofibrosis progresses, the number of white blood cells may increase or decrease, and the number of platelets typically decreases (thrombocytopenia).
Myelofibrosis is uncommon. It may

Develop on its own (called primary myelofibrosis)
Accompany another disorder (called secondary myelofibrosis)

Primary myelofibrosis is myelofibrosis that develops on its own, due to certain genetic mutations. It occurs most often between age 50 and 70 years, mostly in men. About half of people who have primary myelofibrosis have a mutation in the Janus kinase 2 (JAK2) gene. This gene controls certain enzymes that are involved in cell growth and the immune response. Other people have a mutation in the gene called calreticulin (CALR), which is involved in making proteins that are needed for proper cell function, or in the thrombopoietin receptor gene (MPL), which is involved in cell growth.
Secondary myelofibrosis occurs as a result of other disorders, particularly other blood disorders such as chronic myeloid leukemia, polycythemia vera, thrombocythemia, multiple myeloma, and lymphoma. It may also occur in people with tuberculosis, pulmonary hypertension, systemic lupus erythematosus (lupus), systemic sclerosis, and HIV infection, and in people in whom a cancer has spread to the bones.

[Little_Girl]

Progressive fibrosis of the bone marrow, typically associated with pancytopenia and with myeloid metaplasia in other organs.

[Renato]

a condition in which scar tissue grows in the bone marrow so that not enough blood cells are produced for the body