anisocytose

Anisocytosis is a hematologic term describing a wide variation in the sizes of circulating red blood cells (RBCs). It is usually detected as an increased red cell distribution width (RDW) on a complete blood count and may appear on a peripheral blood smear as cells of different sizes. It is a non-specific finding and does not diagnose a particular disease.

Anisocytosis occurs in many conditions that affect RBC production or survival. Common causes include iron deficiency anemia, megaloblastic anemias from vitamin B12 or folate deficiency, sideroblastic anemia, thalassemia, and mixed nutritional deficiencies. Hemolytic anemias, liver disease, chronic inflammation, alcohol use, and recent transfusion can also contribute. Reticulocytosis, the presence of larger immature red cells, can increase size variation.

Diagnosis relies on the RDW value, reported by automated hematology analyzers, and on examination of the peripheral smear. RDW is typically expressed as RDW-CV; higher values indicate greater variation in RBC size. A normal RDW with macrocytosis or microcytosis can occur in some disorders, while a high RDW with normal or abnormal mean corpuscular volume suggests mixed populations or evolving deficiencies. The finding should be interpreted in the context of other red blood cell indices and clinical information.

Management focuses on the underlying cause. Iron, B12, or folate supplementation for deficiencies; treatment of liver disease or inflammatory conditions; avoidance of alcohol; and management of hemolysis when present. In severe symptomatic anemia, red blood cell transfusion may be initiated while definitive therapy is pursued.

Prognosis: Anisocytosis is not a disease by itself; it serves as a clue to etiology and can aid in monitoring response to treatment in some conditions.