In polycythemia vera, the primary problem is an overabundance of red blood cells. The patient must be fully evaluated to make sure that the increase in the red blood cell volume is not due to some other underlying problem. The abundance of red blood cells leads to an increase in blood viscosity (thickness), which may cause thrombosis (blood clots) in the legs, heart, brain or other parts of the body. Removal of blood (phlebotomy) is the primary way to treat this problem. Often patients have too many platelets (small particles in the blood that help in blood clotting) as well, and sometimes the platelet count has to be reduced. Medications such as Anagrelide, Hydroxyurea or Interferon may be used to reduce the platelet count. These drugs may also decrease the need for phlebotomies. In some patients, spleen size may have to be reduced with medications (e.g., Hydroxyurea or Interferon); occasionally the spleen may have to be removed.

In essential thrombocytosis, the patient’s bone marrow produces an excess of platelets. Too many platelets may lead to thrombotic complications. In some patients, treatment need not be instituted immediately, but in others treatment may be urgent. Anagrelide, Hydroxyurea or Interferon can be used to lower platelet counts. In this condition, as in polycythemia vera, some patients may have poorly functioning platelets resulting in abnormal bleeding.

In idiopathic myelofibrosis, the blood-forming cells are abnormal. As a result, their progeny are also abnormal. Some of the abnormal cells (especially megakaryocytes and their progeny, the platelets) may produce cell products that cause scar tissue (fibrosis) in the marrow. The blood-forming cells may also migrate to and reproduce in other organs, such as the liver and spleen. This leads to enlargement of those organs. The spleen may become massively enlarged. Patients usually are anemic and may have abnormal platelet counts (high or low). Treatment depends on the individual patient’s condition. It may include medications to shrink the spleen and lower platelet counts and medications to boost red blood cell production; in some cases, stem cell transplantation may be indicated. Removal of the spleen may be beneficial in those patients who have major symptoms related to the enlarged spleen or who have low blood counts because of a big spleen.