High erythrocyte and leukocyte counts refer to higher than normal counts of both erythrocytes and leukocytes in the peripheral blood. There are several clinical reasons for high erythrocyte and white blood cell counts. For example, in patients with long-term chronic hypoxic diseases, such as chronic obstructive pulmonary disease or congenital cyanotic heart disease, the erythropoietin concentration in the body increases due to long-term hypoxia, and the number of erythrocytes increases significantly. If the patient develops a significant infection, the number of white blood cells will again be increased. At this time, blood tests will show high levels of both red blood cells and white blood cells. In addition, patients with myeloproliferative disorders, such as true erythroid syndrome, may have abnormally high red blood cell counts, but some patients also have abnormally high white blood cell counts, which can lead to high red and white blood cell counts.