myelofibrosis

a disease, the cause of which is unknown, in which FIBROSIS takes place within the BONE MARROW , and many immature red and white blood cells (see ERYTHROCYTE , LEUCOCYTE ) appear in the circulation because of the resulant ANAEMIA . There is an enlargement of the SPLEEN , and blood-producing ( MYELOID ) tissue is abnormally found both here and in the LIVER .