Introduction

As its name implies, Microcytic Anemia refers to a collection of disorders with a red blood cell morphology that predominates with microcytic or small red blood cells.

When viewed on a Wright or Wright-Giemsa stained blood smear, normal red blood cells will have a diameter of 7-8 microns and a mean corpuscular volume (MCV) of 80-100 fL.

Microcytic red blood cells will be less than 7 microns with an MCV of less than 80 fL. Depending on the laboratory policies, anemia will be classified as microcytic when the MCV is less than 80 fL.^5,6 In a majority of cases of microcytic anemia, they will also be hypochromic (cells with too little hemoglobin as represented by an MCHC of less than 32%).

The first image shows an example of normocytic/normochromic cells, normal size and hemoglobin concentration represented by MCV and MCHC within reference ranges, followed by microcytic/hypochromic red blood cells. Finding a normal lymphocyte in the field can help determine RBC size as normal red blood cells are approximately the size of a small lymphocyte nucleus.

Worldwide microcytic anemia is a significant concern with a majority of cases resulting from iron deficiency affecting about two billion people, particularly in women of childbearing age and children.⁸ Anemia of chronic inflammation (ACI or AI) follows and is difficult to statistically represent due to frequent coexisting conditions with iron deficiency.⁹