Microcytosis is a term used to describe red blood cells that are smaller than normal. When observed under the microscope on a blood smear, microcytosis is reported as “slight” to ++++ (“four plus”). This observation helps in diagnosing and distinguishing between different types of anemia, which can be considered microcytic, normocytic or macrocytic, depending on the size of the red blood cells. A low MCV (mean corpuscular volume) can also indicate microcytosis.
The most frequent causes of microcytic anemia are iron deficiency, a chronic inflammatory condition, blood loss from the digestive tract or uterus, and certain genetic abnormalities affecting the production of hemoglobin (thalassemia).