Anemia

Anemia (U.S. spelling) or anaemia is the most common blood disorder. It is caused by not having enough red blood cells or hemoglobin in the blood.

Blood film with iron deficiency anemia.

Sickle cell anemia. Normal red blood cells are shown in Figure 1; with sickle cell anemia, red blood cells look like figure 2

Types (and causes) of anemia according to size of red blood cells

Microcytic anemia

Microcytic anemia develops when red blood cells are smaller than usual because they don’t contain enough hemoglobin. Hemoglobin is a protein in red blood cells responsible for carrying oxygen to different parts of the body.

• Iron deficiency anemia is the most common type of anemia overall
• Hemoglobinopathies—much rarer
  • Sickle-cell disease (once called sickle-cell anemia)
  • Thalassemia

Normocytic anemia

Normocytic anemia occurs when the number of red blood cells is lower than normal, and those cells contain less hemoglobin than they should. This type of anemia is often caused by an underlying chronic condition. Treatment for normocytic anemia typically involves addressing the underlying illness.

• Acute blood loss
• Anemia of chronic disease
• Aplastic anemia (bone marrow failure)

Macrocytic anemia

Macrocytic anemia is a blood condition where the bone marrow produces unusually large red blood cells. These oversized cells lack the necessary nutrients to function properly. While macrocytic anemia itself is not a severe condition, it can lead to serious health complications if left untreated.

• Megaloblastic anemia due to not having enough of either vitamin B12 or folic acid (or both)
• Pernicious anemia is an autoimmune problem with the parietal cells of the stomach
• Alcoholism
• Methotrexate, zidovudine, and other drugs that stop DNA replication. This is the most common cause in nonalcoholic patients.

Dimorphic anemia

Dimorphic anemia includes two types of anemia at the same time. For example, macrocytic hypochromic, due to hookworm infestation leading to not enough of both iron and vitamin B12 or folic acid or following a blood transfusion.