Anemia

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

Structures of hemoglobin forms.

Illustration of backbonding in metal-CO complexes, including hemoglobin (which would lead to carbon monoxide poisoning).

This image shows the heme groups of human hemoglobin in the oxy form. The oxygen ligand binds to the iron metal center of the heme group. There is steric crowding around the O2 ligand that is responsible to prevent carbon monoxide ligand from binding.

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

Normal concentrations of hemoglobin in human blood with respect to age groups.

Microcytic anemia

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

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

Normocytic anemia

Normocytic anemia occurs when the number of red blood cells is lower than normal, and those cells have 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.

• Alcoholism
• Pernicious anemia is an autoimmune problem with the parietal cells of the stomach
• Megaloblastic anemia due to not having enough of either vitamin B12 or folic acid (or both)
• 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.