Polychromasia is a condition in which red blood cells appear grayish-blue in color upon examination under a microscope, explains Nursing Times. Polychromasia occurs when the body releases red blood cells prematurely from the bone marrow. This occurs in response to a certain type of hormone stimulation that results from anemia or due to structural damage to the bone marrow.
Anemia, one of the causes of polychromasia, can be the result of either overproduction or underproduction of red blood cells as well as the production of defective blood cells, according to Nursing Times. Erythropoetin, a hormone produced by the kidneys, controls the production of the red blood cells as well as the rate at which the body releases them from the bone marrow. When the levels of erythropoetin rise, it signals the premature release of red blood cells into the bloodstream, leading to polychromasia.
Polychromasia can also occur when there is damage to the bone marrow, also leading to the premature release of red blood cells, notes Nursing Times. The most common cause of bone marrow damage is infiltration by malignant cells, either from leukemia or as the result of metastasis from other tissue. Another cause is bone marrow fibrosis, in which uncontrollable growth of immature blood cells of various types leads to the formation of scar tissue that damages the bone.