Deb Smith, age 56, came to her nurse practitioner (NP) with fatigue, pallor, dyspnea on exertion, and palpitations. Her laboratory report indicates that her hematocrit, hemoglobin, and reticulocyte counts are low; that her MCV is high; and that her MCH and MCHC are normal. Her diagnosis is pernicious anemia. Answer the following questions regarding Deb’s anemia and provide the pathophysiology associated with the body’s response to this disease process.
Pernicious anemia is a type of megaloblastic anemia that is characterized by the insufficient production of red blood cells due to a lack of vitamin B12. In the case of Deb Smith, the symptoms she is experiencing, such as fatigue, pallor, dyspnea on exertion, and palpitations, are consistent with the clinical presentation of pernicious anemia.
The laboratory reports indicate several abnormalities in Deb’s blood parameters which further support the diagnosis of pernicious anemia. Her hematocrit, hemoglobin, and reticulocyte counts are low, suggesting a decrease in the number of circulating red blood cells. This reduction in red blood cell mass leads to a decrease in the oxygen-carrying capacity of the blood, resulting in fatigue and dyspnea on exertion. Deb’s high mean corpuscular volume (MCV) indicates macrocytic red blood cells, meaning that the red blood cells are larger than normal. This is a characteristic feature of megaloblastic anemias, including pernicious anemia. Additionally, her mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) are within the normal range, which suggests that the content of hemoglobin in each red blood cell is normal.
The underlying cause of pernicious anemia is a deficiency in vitamin B12, which is essential for the synthesis of DNA and the maturation of red blood cells in the bone marrow. Vitamin B12 is typically obtained from animal-derived foods or through the binding of intrinsic factor, a protein secreted by the gastric parietal cells. Intrinsic factor facilitates the absorption of vitamin B12 in the small intestine.
In the case of pernicious anemia, the primary cause of the deficiency is the autoimmune destruction of the gastric parietal cells, impairing the production of intrinsic factor. This autoimmune destruction is thought to be mediated by the production of antibodies against gastric parietal cells or against intrinsic factor itself. Without intrinsic factor, Deb is unable to absorb vitamin B12 efficiently, leading to a deficiency.
The deficiency of vitamin B12 results in several pathophysiological changes in the body. Vitamin B12 is required for the normal division and maturation of red blood cells in the bone marrow. Without sufficient vitamin B12, the cells in the bone marrow cannot replicate properly, resulting in the production of abnormally large and immature red blood cells known as megaloblasts. These megaloblasts are larger in size and have a shorter lifespan than mature red blood cells, leading to a decreased red blood cell count and subsequent anemia.
Furthermore, the decreased production of red blood cells leads to ineffective erythropoiesis. Ineffective erythropoiesis refers to the impaired production of red blood cells despite the adequate availability of iron, folate, and other necessary components. The combination of decreased red blood cell production and increased destruction of megaloblasts in the bone marrow contributes to the macrocytic anemia seen in pernicious anemia.
Deb’s symptoms of fatigue, pallor, dyspnea on exertion, and palpitations can be explained by the reduced oxygen-carrying capacity of her blood due to the decreased number of red blood cells. The macrocytic red blood cells are unable to efficiently transport oxygen, leading to tissue hypoxia and subsequent fatigue. The decreased number of red blood cells also affects the transportation of carbon dioxide, impairing the body’s ability to remove waste products efficiently. Furthermore, the stimulation of the bone marrow to produce more red blood cells in response to the anemia leads to an increased workload on the heart, resulting in palpitations.
In conclusion, Deb’s symptoms and laboratory results are consistent with the diagnosis of pernicious anemia. The underlying pathophysiology involves the autoimmune destruction of the gastric parietal cells, leading to a deficiency in vitamin B12 and subsequent abnormalities in red blood cell production and maturation. These changes result in macrocytic anemia and the associated symptoms of fatigue, pallor, dyspnea on exertion, and palpitations.