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pernicious anemia; autoimmune gastritis

Etiology: 1) autoimmune 2) associated autoimmune diseases a) Grave's disease b) myxedema c) thyroiditis d) adrenocorticial insufficiency e) vitiligo f) hypoparathyroidism g) diabetes mellitus type-1 Epidemiology: 1) most common cause of vit B12 deficiency in temperate climates 2) occurs most frequently in patients of northern European descent & African Americans 3) much less common in southern Europeans & Asians 4) men & women equally affected 5) it is a disease of the elderly a) average age of presentation is 60 years b) rare in individuals < 30 years of age Pathology: 1) complement fixing antibodies against parietal cell surface antigen(s) 2) cellular immune response likely involved* 3) atrophy of gastric mucosa (autoimmune atrophic gastritis) a) affects the acid & pepsin-secreting part of the stomach b) the antrum is spared c) cellular atypia in gastric cytology specimens 4) failure to secrete intrinsic factor 5) inability to absorb vitamin B12 * pernicious anemia is unusually common in patients with agammaglobulinemia Genetics: - relatives of patients with pernicious anemia have an increased incidence of the disease Clinical manifestations: 1) primarily those of vitamin B12 deficiency - lower extremity paresthesias 2) scattered areas of skin hypopigmentation suggestive of vitiligo 3) insidious in onset 4) slowly progressing Laboratory: 1) antiparietal cell autoantibodies (90%)* 2) anti-intrinsic factor autoantibodies (60%)# (not indicated) [3] 3) increased levels of serum gastrin 4) complete blood count shows macrocytic anemia of vit B12 deficiency 5) bone marrow biopsy shows megaloblastic changes of vit B12 deficiency 6) pentagastrin stimulation test shows resistant achlorhydria * antiparietal cell autoantibodies are found in 50% of individuals with gastric atrophy without pernicious anemia # more specific than antiparietal cell autoantibodies; do not perform anti-intrinsic factor autoantibodies testing for diagnostic purposes [3] Special laboratory: - upper GI endoscopy - surveillance for gastric carcinoma & gastric carcinoid tumors [6] Complications: - gastric polyps & 2-fold risk of gastric cancer & carcinoid tumors - associated with development of carcinoid, but predisposition to gastric adenocarcinoma controversial [7] Differential diagnosis: - celiac disease (diarrhea, iron-deficiency anemia) Management: 1) lifelong parenteral vit B12 replacement 2) surveillance for gastric cancer with fecal occult blood 3) treatment with glucocorticoids may reverse the disease clinically & pathologically

Related

vitamin B12 deficiency

General

megaloblastic anemia autoimmune disease atrophic gastritis

References

  1. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 655-56
  2. UpToDate 14.1 http://www.utdol.com
  3. Medical Knowledge Self Assessment Program (MKSAP) 16, 18. American College of Physicians, Philadelphia 2012, 2018,
  4. Lahner E, Annibale B. Pernicious anemia: new insights from a gastroenterological point of view. World J Gastroenterol. 2009 Nov 7;15(41):5121-8. Review. PMID: 19891010
  5. NEJM Knowledge+ Gastroenterology
  6. Rustgi SD, Bijlani P, Shah SC. Autoimmune gastritis, with or without pernicious anemia: epidemiology, risk factors, and clinical management. Therap Adv Gastroenterol. 2021;14:17562848211038771. PMID: 34484423
  7. Miceli E, Lenti MV, Gentile A et al. Long-term natural history of autoimmune gastritis: Results from a prospective monocentric series. Am J Gastroenterol 2024 May; 119:837 PMID: 38050966 https://journals.lww.com/ajg/abstract/2024/05000/long_term_natural_history_of_autoimmune_gastritis_.17.aspx