Polycythemia is a rare disorder of the bone marrow that causes the overproduction of all three blood cell lines: white blood cells, red blood cells and platelets. The causes of this disorder are still investigated. There is some evidence that polycythemia results from primary pathologic processes such as cardiovascular disease or kidney problems, including tumors or bone marrow diseases. The disease usually develops slowly, and most patients do not have clinical signs. There are several types of polycythemia: primary, secondary adequate, and secondary inadequate polycythemia. Primary polycythemia can be a primary bone marrow disorder called polycythemia vera. Signs may include excessive thirst and urination, bleeding from small capillaries, and neurological disturbances due to increased density of blood. Secondary polycythemia is stimulated by lack of oxygen and may occur with primary heart or lung disease or methemoglobinemia (e.g., acetaminophen intoxication in cats). Secondary polycythemia can also occur with kidney tumors.2 Patients with polycythemia vera have an increased tendency to form blood clots that can result in strokes or heart attacks. Some can develop bluish skin discoloration, exercise intolerance, red skin spots, tremors, seizures, difficulty breathing, lethargy, and uveitis.1 Puppies with this condition feed poorly and fail to thrive.1

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Treatment includes phlebotomy which may need to be repeated at 2-3 month intervals. Chemotherapy using chlorambucil may be effective. Dogs with secondary inadequate polycythemia have apathy, gait disturbances and disorientation, and seizures which are most probably due to the formation of blood clots leading to low level of blood oxygen. Even after emergency treatment the general state deteriorates leading to blood infections (sepsis). Dogs with secondary complications have a poor prognosis and are euthanized.

polycythemia vera - a disorder of the bone marrow that causes the overproduction of all three blood cell lines: white blood cells
uveitis - inflammation of part or all of the uvea that involves sclera, cornea, and retina
phlebotomy - the techniques used to draw blood from a vein for diagnostic purposes or for treatment of certain blood disorders such as erythrocytosis, hemochromatosis, polycythemia vera, and porphyria cutanea tarda


  1. Journal of Veterinary Behavior: Clinical Applications and Research Volume 1, Issue 1, July 2006, Pages 23-28
  2. Ancillary Notes for Clinical Hematology (Washington State University, College of Veterinary Medicine)

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