Pathophysiology of Iron Deficiency and Pernicious Anemia

            Anemia is a reduction of erythrocytes or a decrease in the quality or quantity of hemoglobin (Huether & McCance, 2017). Because of the reduced oxygen-carrying capacity of the blood, those with anemia may suffer from fatigue, shortness of breath, dizziness, and tachycardia. Iron deficiency anemia (IDA) is the most common type of anemia in the world (Hammer & McPhee, 2019; Huether & McCance, 2017). IDA arises from wither lack of dietary intake of iron, blood loss, or both (Huether & McCance, 2017). First, iron stores are depleted, and healthy red cell production continues. Then, iron-deficient red cell production begins when there are insufficient amounts of iron in bone marrow (Huether & McCance, 2017). Finally, hemoglobin-deficient red cells enter circulation and replace healthy red cells (Huether & McCance, 2017).

            Pernicious anemia (PA) is a macrocytic anemia caused by vitamin B12 deficiency (Hammer & McPhee, 2019; Huether & McCance, 2017). Vitamin B12 is required for maturation and DNA synthesis of red cells. Those with PA lack or have insufficient amounts of intrinsic factor, which is needed for gastric absorption of vitamin B12 (Huether & McCance, 2017). Most cases of PA are caused by autoimmune gastritis, which destroys parietal cells and diminishes the production of intrinsic factor (Huether & McCance, 2017). The result is red cells that do not divide properly and are too large (National Institutes of Health, n.d.). This reduces the oxygen-carrying capacity of the blood.

            Both IDA and PA lead to reduced oxygen-carrying capacity of the blood. They differ in the pathologic mechanism. IDA results in lack of iron, and PA is from the malabsorption of vitamin B12. IDA is usually caused by a lack of dietary iron or chronic blood loss, whereas PA thought to be mostly autoimmune and sometimes congenital (Huether & McCance, 2017). Both types cause weakness and fatigue (Huether & McCance, 2017). Other IDA symptoms can include pale earlobes, palms, and conjunctivae, and even changes to the epithelial tissue (Huether & McCance, 2017). PA can produce a sore tongue, weight loss, and neurological manifestations due to nerve demyelination (Huether & McCance, 2017). Risk factors for IDA are living in poverty, women of childbearing age, and children (Huether & McCance, 2017). Congenital intrinsic factor deficiency is autosomal recessive, and about 30% of those with autoimmune PA also have a relative with it (Huether & McCance, 2017). First-degree female relatives are especially at risk (Huehter & McCance, 2017).

How Patient Factors May Influence the Disorders

            As stated before, children are at risk for IDA. In contrast, PA takes 20-30 years to develop and would not usually be seen until about 60 years of age (Huether & McCance, 2017; National Organization for Rare Disorders (NORD), 2019). PI is seen more among whites from northern Europe, Scandinavia, and North America (NORD, 2019). Those in developing countries are more at risk for IDA due to lack of dietary iron and chronic parasitic infections (Huether & McCance, 2017). Females experience both IDA and PA more often (Huether & McCance, 2017). A bone marrow biopsy can diagnose both Blood tests such as serum ferritin and total iron-binding capacity for IDA, and serum methylmalonic acid and homocysteine for PA can be useful (Huether & McCance, 2017).


Hammer, G.D., & McPhee, S.J. (2019). Pathophysiology of disease: An introduction to clinical  

            clinical medicine (6th ed.). New York: NY: McGraw-Hill Education.

Huether, S.E., & McCance, K.L. (2017). Understanding pathophysiology (6th ed.). St. Louis,

            MO: Mosby. 

National Institutes of Health. (n.d.). Pernicious anemia. Retrieved on July 6, 2019 from

National Organization for Rare Disorders. (2019). Anemia, pernicious. Retrieved from