megakaryocytosis


polycythemia

 [pol″e-si-the´me-ah] an increase in the total red blood cell mass of the blood; called also erythrocythemia, hypercythemia, and hypererythrocythemia.
There are two distinct forms of the disease: Primary polycythemia (polycythemia vera) is a myeloproliferative disorder of unknown etiology. It is characterized by hyperplasia of the cell-forming tissues of the bone marrow, with resultant elevation of the erythrocyte count and hemoglobin level, and an increase in the number of leukocytes and platelets.
Secondary polycythemia is a physiologic condition resulting from a deficient oxygen supply to the tissues. The body attempts to compensate for the deficiency by manufacturing more hemoglobin and erythrocytes. Living at high altitudes can produce polycythemia, as can severe chronic lung and heart disorders, especially congenital heart defects.
Absolute polycythemia refers to an increase in red cell mass from any cause. Relative polycythemia refers to a loss of plasma volume causing an elevated hematocrit.Symptoms. The symptoms of primary and secondary polycythemia are much the same. The increased erythrocyte production results in thickening of the blood and an increased tendency toward clotting. The viscosity of the blood limits its ability to flow properly, so that the supply to the brain and other vital tissues is diminished. This may cause sluggishness, irritability, headache, dizziness, fainting, disturbances of sensation in the hands and feet, and a feeling of fullness in the head. There may be episodes of acute pain as spontaneous clots occur in the blood vessels. The spleen becomes enlarged and the smaller veins become more prominent, so that the skin has a bluish hue. The secondary form is often accompanied by enlargement of the tips of the fingers (clubbing).Treatment. Treatment of polycythemia vera is aimed at reducing the red cell count and decreasing the blood volume. Mild cases can be managed by periodic phlebotomy. More serious cases may require myelosuppressive therapy; interferon and large-dose aspirin therapy may also be used. Research on treatment modalities is ongoing. In secondary polycythemia, successful treatment of the causative illness will relieve the polycythemia.

megakaryocytosis

(mĕg″ă-kăr″ē-ō-sī-tō′sĭs) [″ + ″ + ″ + osis, condition] An increased number of megakaryocytes in the bone marrow; presence of megakaryocytes in the blood.

megakaryocytosis

An increase in the number of MEGAKARYOCYTES in the bone marrow.