What does polychromasia indicate about red blood cells?

Polychromasia refers to the presence of red blood cells (RBCs) that exhibit a varied staining color when viewed under a microscope, indicating that these cells are not fully mature. This condition suggests that the bone marrow is responding to a demand for more red blood cells, often in the context of anemia.

When anemia occurs, the bone marrow is stimulated to produce more red blood cells, leading to the release of younger, less mature cells into the bloodstream. These immature RBCs, which are often slightly larger and may retain more RNA than their fully mature counterparts, exhibit a basophilic (blue hue) color change due to the presence of reticulocytes, which are the precursor cells to mature red blood cells. Therefore, a finding of polychromasia is interpreted as a sign of the bone marrow's adaptive response to anemia, where it is trying to compensate for a lower-than-normal count of healthy RBCs.