Autoimmune gastritis

Autoimmune gastritis (AIG) is a form of atrophic gastritis characterized by the autoimmune destruction of parietal cells. The condition is frequently associated with other autoimmune disorders (e.g., Hashimoto thyroiditis, type 1 diabetes mellitus). The destruction of parietal cells leads to achlorhydria (which results in impaired iron absorption) and hypergastrinemia, while the loss of intrinsic factor impairs vitamin B₁₂ absorption. Common clinical features include dyspepsia, epigastric pain, and nausea, as well as features of anemia. Diagnosis is supported by serological testing for antiparietal cell and anti-intrinsic factor antibodies as well as screening for associated autoimmune thyroid diseases. A significant complication of the disease is pernicious anemia due to severe vitamin B₁₂ deficiency; management therefore includes vitamin B₁₂ replacement therapy.

See "Gastric premalignant conditions" for further details on diagnosis and management.

• Prevalence: ∼ 0.5–2.0% ^[1]
• Sex: ♀: ♂ (3:1) ^[2]
• Associated with other autoimmune diseases and with major histocompatibility haplotypes HLA-B8 and HLA-DR3 ^[3]

Epidemiological data refers to the US, unless otherwise specified.

• Autoimmune destruction of the parietal cells in the gastric corpus and fundus (T-cell induced autoantibodies against H⁺/K⁺ ATPase) → achlorhydria → increased release of gastrin (due to loss of negative feedback) → G cell hyperplasia → hypergastrinemia → hyperplasia of enterochromaffin-like cells → ↑ risk of gastric neuroendocrine tumors
• Achlorhydria impairs the intestinal absorption of inorganic iron → iron deficiency anemia (early manifestation of AIG)
• Autoantibodies against intrinsic factor → vitamin B₁₂ deficiency → pernicious anemia

• Dyspepsia
• Epigastric pain
• Heartburn, regurgitation
• Nausea, vomiting
• Abdominal paresthesia
• Features of anemia (e.g., pallor, fatigue): due to iron deficiency and/or vitamin B₁₂ deficiency
• Symptoms of co-existing autoimmune diseases (e.g., goiter in Hashimoto thyroiditis, vitiligo, type 1 diabetes)

• EGD with biopsies
• CBC
• Nutritional deficiency screening (e.g., vitamin B12 level, iron studies)
• AIG serology (e.g., anti-intrinsic factor antibodies, antiparietal cell antibodies)
• Screening for autoimmune thyroid disease
• See "Diagnosis of gastric premalignant conditions" for details.

• Correct nutritional deficiencies, e.g.:
  • Iron therapy for iron deficiency
  • Vitamin B₁₂ replacement therapy
• See also: "Management of gastric premalignant conditions."

• Vitamin B₁₂ deficiency with pernicious anemia
• Gastric neuroendocrine tumor (NET) ^[2]

We list the most important complications. The selection is not exhaustive.