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 Htut2021Toh2016Ammouri2020+3 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 Toh2016Ammouri2020Oo2017. This immune-mediated destruction of parietal cells leads to both intrinsic factor deficiency and reduced gastric acid secretion Toh2016Ammouri2020Esposito2022+1 MORE.
Vitamin B12 Malabsorption and Megaloblastic Anaemia
The loss of intrinsic factor prevents the absorption of dietary vitamin B12, resulting in cobalamin deficiency Htut2021Toh2016Ammouri2020+4 MORE. This deficiency disrupts normal DNA synthesis in red blood cell precursors, causing megaloblastic anaemia—a hallmark of pernicious anaemia Htut2021Ammouri2020Esposito2022+2 MORE. The disease often develops slowly, and patients may acclimatize to symptoms, making early detection challenging Htut2021Ammouri2020Esposito2022.
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 Htut2021Ammouri2020Esposito2022+1 MORE. 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 Toh2016Esposito2022Lahner2009.
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 Ammouri2020Esposito2022Callender1957+1 MORE. 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 Htut2021Ammouri2020Oo2017. Laboratory findings often include megaloblastic anaemia, low serum cobalamin, elevated serum gastrin, and the presence of parietal cell and intrinsic factor antibodies Toh2016Ammouri2020Oo2017+1 MORE. However, some patients may present with normal or high cobalamin levels or atypical blood findings, complicating the diagnosis Htut2021Ammouri2020Oo2017.
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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