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[Conditions](https://durgical.com/en/conditions/) · [Vitamins and minerals](https://durgical.com/en/conditions/)

# Pernicious anaemia

An autoimmune disease that destroys the [stomach](https://durgical.com/en/anatomy/stomach/) cells making intrinsic factor; without it vitamin B12 cannot be absorbed.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Stomach](https://durgical.com/en/anatomy/stomach/)
- [Ileum](https://durgical.com/en/anatomy/ileum/)
- [Tongue](https://durgical.com/en/anatomy/tongue/)
- [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/)

## In biochemistry

- [Cobalamin (vitamin B12)](https://durgical.com/en/biochemistry/topics/cobalamin/)

## In immunology

- [Type II hypersensitivity (antibody against cells)](https://durgical.com/en/immunology/type-ii-hypersensitivity/)
- [Autoantibodies: the table to know](https://durgical.com/en/immunology/autoantibodies-the-table-to-know/)

## In histology

- [Hematopoiesis and bone marrow](https://durgical.com/en/histology/hematopoiesis-and-bone-marrow/)
- [Stomach: gastric glands, parietal and chief cells](https://durgical.com/en/histology/stomach-gastric-glands-parietal-and-chief-cells/)

## In the clinical exam

- [Anemia syndrome](https://durgical.com/en/clinical-exam/anemia-syndrome/)

## In physiology

- [Anemia physiology and compensation](https://durgical.com/en/physiology/anemia-physiology-and-compensation/)
- [Gastric acid secretion](https://durgical.com/en/physiology/gastric-acid-secretion/)
- [Absorption of iron, calcium and vitamin B12](https://durgical.com/en/physiology/absorption-of-iron-calcium-and-vitamin-b12/)
- [Patterns of malabsorption](https://durgical.com/en/physiology/patterns-of-malabsorption/)
- [Vitamins and minerals: a physiological overview](https://durgical.com/en/physiology/vitamins-and-minerals-a-physiological-overview/)

## Why it happens

- [Vitamin deficiencies: what each one does to tissue](https://durgical.com/en/general-pathology/vitamin-deficiencies-what-each-one-does-to-tissue/)
- [Precancerous conditions: when chronic inflammation, metaplasia or hyperplasia raise the risk](https://durgical.com/en/general-pathology/precancerous-conditions-when-chronic-inflammation-metaplasia-or-hyperplasia-rais/)

## What it is

Autoimmune atrophic gastritis of the gastric body and fundus with loss of parietal cells and intrinsic factor, leading to vitamin B12 deficiency, megaloblastic anaemia and nerve damage.

## Who gets it

The most common cause of severe B12 deficiency in adults, especially after age 60 and in women. It is linked to other autoimmune diseases.

## Causes

- Antibodies to the parietal-cell H⁺/K⁺-ATPase
- Antibodies to intrinsic factor (block its binding to B12)
- Genetic and autoimmune predisposition

## Risk factors

- Age over 60
- Hashimoto thyroiditis, Graves disease, type 1 diabetes, vitiligo, Addison disease
- Family history
- Northern European ancestry

## Pathophysiology

T cells and antibodies destroy parietal cells: acid (achlorhydria) and intrinsic factor are lost. Without intrinsic factor B12 is not absorbed in the terminal [ileum](https://durgical.com/en/anatomy/ileum/) and, after years of draining [liver](https://durgical.com/en/anatomy/liver/) stores, methionine synthase fails (megaloblastic anaemia through the folate trap) and so does methylmalonyl-CoA mutase (myelin damage). Achlorhydria raises gastrin, which stimulates enterochromaffin-like cells: risk of gastric carcinoid tumours. Iron absorption also falls.

## Symptoms and signs

- Tiredness, pallor with a yellow tint, breathlessness
- Smooth, red, sore [tongue](https://durgical.com/en/anatomy/tongue/)
- Tingling and numbness of feet and hands, unsteady walking
- Memory loss, depression, irritability
- Loss of appetite and weight

## Red flags

- Ataxia, leg weakness or sphincter problems
- Confusion or psychosis
- Severe anaemia with cardiac symptoms

## Diagnosis

**Clinical**
Macrocytic anaemia or neurological symptoms in an adult, often with another autoimmune disease.

**Tests**
Low serum B12, high methylmalonic acid and homocysteine; antibodies to intrinsic factor (very specific) and to parietal cells (sensitive); high gastrin and low pepsinogen I; blood count with high MCV.

**Imaging**
Upper GI endoscopy with biopsy: atrophy of the gastric body, intestinal metaplasia; spinal MRI if there is myelopathy.

## Treatment

**Medical**
Lifelong vitamin B12, intramuscular or high-dose oral

**Follow-up**
Blood count, potassium and reticulocytes at the start; periodic B12 and thyroid checks

**Follow-up**
Surveillance endoscopy according to the risk of gastric cancer and carcinoid tumours

**Rehabilitation**
Physiotherapy if neurological deficits remain

## Drugs for this condition

- [Cyanocobalamin](https://durgical.com/en/pharmacology/cyanocobalamin/)
- [Hydroxocobalamin](https://durgical.com/en/pharmacology/hydroxocobalamin/)

## Complications

- Subacute combined degeneration of the [spinal cord](https://durgical.com/en/anatomy/spinal-cord/)
- Gastric cancer and gastric carcinoid tumours
- Associated iron deficiency
- Reversible dementia if treated early

## Prognosis

With lifelong B12 the anaemia corrects fully; nerve damage improves if treated early but may persist.

## Prevention

- Not preventable; early detection avoids nerve damage

## Test yourself

Think of the answer, then tap the question to see it.

## What does the autoimmunity destroy in pernicious anaemia?

The parietal cells of the gastric body and fundus, which make acid and intrinsic factor.

## Which antibody is most specific for pernicious anaemia?

Anti-intrinsic factor antibody; anti-parietal cell antibody is more sensitive but less specific.

## Why can high-dose oral B12 treat it?

A small fraction of B12 is absorbed by passive diffusion along the gut, without intrinsic factor.

## Why is the risk of gastric carcinoid tumours higher?

Achlorhydria raises gastrin, which drives proliferation of enterochromaffin-like cells.

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## Related conditions

- [Megaloblastic anaemia (B12 or folate deficiency)](https://durgical.com/en/conditions/megaloblastic-anaemia/)
- [Helicobacter pylori gastritis](https://durgical.com/en/conditions/helicobacter-pylori-gastritis/)
- [Gastric cancer](https://durgical.com/en/conditions/gastric-cancer/)
- [Hypothyroidism](https://durgical.com/en/conditions/hypothyroidism/)
- [Type 1 diabetes mellitus](https://durgical.com/en/conditions/type-1-diabetes-mellitus/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Pernicious anemia: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000569.htm) (MedlinePlus, US National Library of Medicine, 2026); [Vitamin B12: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/002403.htm) (MedlinePlus, US National Library of Medicine, 2026); [Vitamin B12 level: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003705.htm) (MedlinePlus, US National Library of Medicine, 2026); [Methylmalonic Acid (MMA) Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/methylmalonic-acid-mma-test/) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Source: https://durgical.com/en/conditions/pernicious-anaemia/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/pernicious-anaemia/