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Anti-intrinsic factor antibodies
Anti-parietal cell antibodies
May also have positive ANA or antibodies linked to other autoimmune conditions
Stomach (gastric parietal cells)
Blood and nervous system (as a result of B12 deficiency)
Pernicious anemia is a chronic autoimmune condition in which the body cannot absorb enough vitamin B12, a vital nutrient required to make healthy red blood cells. The immune system attacks the stomach lining and intrinsic factor, a protein necessary for B12 absorption in the small intestine.
Without B12, the body can’t make enough healthy red blood cells, which leads to anemia and sometimes nerve damage if left untreated.
Fatigue
Weakness
Pale or yellowish skin
Shortness of breath
Dizziness
Numbness or tingling in hands and feet
Poor balance or coordination
Memory issues or brain fog
Mood changes or depression
Swollen, sore tongue (glossitis)
Mouth ulcers
Loss of appetite
Weight loss
Pernicious anemia is caused by an autoimmune attack on:
Parietal cells in the stomach (which produce intrinsic factor)
Intrinsic factor itself – a protein essential for vitamin B12 absorption
Without intrinsic factor, vitamin B12 from food cannot be absorbed properly. Other risk factors include:
Family history of autoimmune diseases
Type 1 diabetes, Hashimoto’s, or vitiligo
Older age
Northern European ancestry
Diagnosis may include:
Complete blood count (CBC) – shows large red blood cells (megaloblastic anemia)
Vitamin B12 level – low in the blood
Intrinsic factor antibody test – often positive
Parietal cell antibody test
Methylmalonic acid (MMA) and homocysteine – often elevated
Vitamin B12 injections – often given regularly for life
High-dose oral B12 supplements (in some cases)
Monitoring for neurological symptoms
Treating underlying autoimmune gastritis if present
Early treatment often leads to full recovery, especially if nerve symptoms are caught quickly.
Excellent with early treatment
Neurological symptoms may become permanent if untreated for too long
Long-term B12 maintenance therapy is needed
May be linked to higher stomach cancer risk, so ongoing care is important
Affects approximately 0.1% of the general population, up to 2% in people over 60
More common in Northern Europeans, women, and people with autoimmune disorders
National Heart, Lung, and Blood Institute. (2022). Pernicious Anemia.
https://www.nhlbi.nih.gov/health/pernicious-anemia
Stabler, S. P. (2013). Pernicious Anemia and Other Causes of Vitamin B12 Deficiency. New England Journal of Medicine, 368(2), 149–160.
https://doi.org/10.1056/NEJMra1113996
Office of Dietary Supplements – NIH. (2021). Vitamin B12 Fact Sheet.
https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
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