Pernicious anaemia pathophysiology
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Autoimmune Gastritis and Intrinsic Factor Deficiency in Pernicious Anaemia Pathophysiology
Pernicious anaemia is primarily an autoimmune disease that targets the stomach’s parietal cells, leading to chronic atrophic gastritis and the loss of intrinsic factor, a protein essential for vitamin B12 (cobalamin) absorption in the terminal ileum 1234+2 MORE. The autoimmune process is driven by the activation of Th1 CD4 T cells against the gastric H/K ATPase, resulting in the production of parietal cell antibodies and, in many cases, intrinsic factor antibodies 237. This immune-mediated destruction of parietal cells leads to both intrinsic factor deficiency and reduced gastric acid secretion 2349.
Vitamin B12 Malabsorption and Megaloblastic Anaemia
The loss of intrinsic factor prevents the absorption of dietary vitamin B12, resulting in cobalamin deficiency 1234+3 MORE. This deficiency disrupts normal DNA synthesis in red blood cell precursors, causing megaloblastic anaemia—a hallmark of pernicious anaemia 1348+1 MORE. The disease often develops slowly, and patients may acclimatize to symptoms, making early detection challenging 134.
Systemic and Neurological Complications
Vitamin B12 deficiency in pernicious anaemia can lead to a wide range of systemic effects, including neurological symptoms that may become irreversible if not treated promptly 1347. Severe anaemia can also increase the risk of cardiovascular complications, such as ischemic hepatopathy (shock liver), due to hypoxemia and reduced cardiac output . Other complications include iron deficiency anaemia (due to loss of gastric acid), bone marrow failure, and increased risk of gastric cancer and neuroendocrine tumors 249.
Genetic and Environmental Factors
There is evidence of genetic susceptibility to pernicious anaemia, with familial tendencies and associations with certain constitutional traits and autoimmune disorders, such as autoimmune thyroid disease, type 1 diabetes, and vitiligo 3489. Environmental factors, such as long-standing Helicobacter pylori infection, may also contribute to the development of autoimmune gastritis and subsequent pernicious anaemia .
Diagnostic Challenges
Diagnosing pernicious anaemia can be difficult due to its varied clinical presentations and the limitations of current diagnostic tools 137. Laboratory findings often include megaloblastic anaemia, low serum cobalamin, elevated serum gastrin, and the presence of parietal cell and intrinsic factor antibodies 2379. However, some patients may present with normal or high cobalamin levels or atypical blood findings, complicating the diagnosis 137.
Conclusion
Pernicious anaemia is a complex autoimmune disorder characterized by the destruction of gastric parietal cells, intrinsic factor deficiency, and subsequent vitamin B12 malabsorption. This leads to megaloblastic anaemia and a range of systemic complications, including neurological and cardiovascular effects. Genetic predisposition, environmental triggers, and associations with other autoimmune diseases further contribute to its pathophysiology. Early recognition and treatment are crucial to prevent irreversible complications.
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