Microcytic anemia: Pathology review

At the family medicine center, there is a 60-year-old Indigenous American named Istu who came to visit the doctor because of his progressive fatigue and difficulty in swallowing. Next to him, there is a mother from Greece with her child, Thalia, who is 10 months old. Little Thalia appeared healthy at birth but in the past 2 months, her mother noticed that her face was often pale, she’s been less active, and there was a mass in her belly.

Both Istu and Thalia are suffering from anemia, which is defined as lower than average levels of hemoglobin, typically below 13.5 g/dL in adult men and below 12.0 g/dL in adult women. For children, this level varies based on the age. Now, anemias can be broadly grouped into 3 categories based on mean corpuscular volume, or MCV, which reflects the volume of a Red blood cell or RBC. So microcytic anemia is where the MCV is lower than 80 fL, normocytic, with an MCV between 80 and 100 fL, and macrocytic, with an MCV larger than 100 fL. Now, let’s focus on the microcytic anemias, and the most common causes are iron deficiency anemia, lead poisoning, sideroblastic anemia, and thalassemias. Although microcytic anemia can also present in anemia of chronic disease, which is caused by Inflammatory conditions like rheumatoid arthritis, and systemic lupus erythematosus or SLE, it’s usually classified as normocytic anemia.

Now iron deficiency anemia, lead poisoning, and sideroblastic anemia are caused by defective heme synthesis, while thalassemias are caused by defective globin chains. Normally, RBCs are loaded with millions of copies of a protein called hemoglobin. Hemoglobin is actually made up of four peptide, or globin, chains, each bound to a heme group. Those 4 heme molecules have, right in the middle, iron, which binds to oxygen and allows it to move in our body.

Okay, so let’s look at iron deficiency anemia which could be caused by decreased intake, decreased absorption, increased demand, or increased loss of iron. For your exams, it’s important to know that the clues to help you identify this disorder are often based on the patient’s history. A high yield fact is that the most common cause of iron deficiency is chronic blood loss. This includes women with heavy menstruation or people with bleeding gastric ulcers, and, most importantly, elderly males with colon cancer that can bleed.