Gastritis, Pernicious Anemia

Key Features

• A rare autoimmune disorder involving the fundic glands

  • Decreased intrinsic factor secretion

  • Consequent vitamin B₁₂ malabsorption

• Most patients have malabsorption secondary to chronic Helicobacter pylori infection that results in

  • Atrophic gastritis and achlorhydria

  • Small intestine bacterial overgrowth

  • Insufficient absorption of dietary vitamin B₁₂

• Fundic histology shows severe gland atrophy and intestinal metaplasia

Clinical Findings

• Hypergastrinemia may induce hyperplasia of gastric enterochromaffin-like cells, development of small, multicentric carcinoid tumors in 5%

• Risk of adenocarcinoma is increased threefold

• Prevalence is 1–3%

Diagnosis

• Endoscopy with biopsy

• Achlorhydria leads to pronounced hypergastrinemia (> 1000 pg/mL)

• Anti-intrinsic factor antibodies are present in 70%

• Low serum vitamin B₁₂ level

• Megaloblastic (macrocytic) anemia

Treatment

• One-time endoscopic screening for adenocarcinoma or carcinoids recommended

• Patients with extensive atrophy and metaplasia involving the gastric antrum and body, dysplasia, or small carcinoids require periodic endoscopic surveillance

• Vitamin B₁₂ 100 mcg intramuscularly daily for first week, weekly for first month, then monthly for life if B₁₂ deficiency documented