Essential thrombocythemia is a myeloproliferative disease, that is based upon the disease of a stem cell, which results in a preferred uncontrolled increase of the platelets.
At the beginning of the disease, the symptoms are rather unspecific. A reddening of the face sometimes even gives the impression that the concerned patient would be especially healthy.
Osteomyelofibrosis is a malignant disease of the bone marrow. It is either an independent disease or the terminal stage of another myeloproliferative disease.