Pernicious anemia
The classic autoimmune cause of vitamin B12 deficiency: the immune system attacks the stomach cells that make 'intrinsic factor', the protein needed to absorb B12 from food. It causes a large-cell anaemia and, if untreated, nerve damage — but is very treatable with B12 injections.
What it is
Pernicious anaemia is an autoimmune condition and the classic cause of severe vitamin B12 deficiency. Absorbing B12 from food requires 'intrinsic factor', a protein made by parietal cells in the stomach lining. In pernicious anaemia the immune system attacks these cells (autoimmune gastritis) and produces antibodies against intrinsic factor, so B12 can no longer be absorbed however much is eaten. The result is a slowly developing deficiency causing a macrocytic (large red cell) anaemia and, importantly, damage to the nervous system that can occur even before the anaemia — tingling, numbness, balance and memory problems — some of which becomes permanent if treatment is delayed. It is commoner with age and clusters with other autoimmune conditions (thyroid disease, type 1 diabetes, vitiligo). Because the problem is absorption, not diet, treatment is usually lifelong B12 injections rather than tablets.
Key lab markers
- Vitamin B12 — low; the central abnormality.
- Methylmalonic acid (and homocysteine) — raised, confirming true tissue-level B12 deficiency when B12 is borderline.
- Full blood count and MCV — a macrocytic (large-cell) anaemia is typical.
- Blood film — large red cells and characteristic hypersegmented neutrophils.
- Reticulocytes — low initially; rise after treatment starts (a good sign).
- Intrinsic factor antibodies — specific for pernicious anaemia; parietal cell antibodies are supportive.
- Ferritin, folate, TSH — checked for coexisting deficiencies and autoimmune thyroid disease.
Symptoms
- Tiredness, breathlessness, pallor (from the anaemia)
- Tingling or numbness in the hands and feet
- Balance problems, unsteadiness
- Memory or concentration difficulty, low mood
- A sore, smooth, red tongue; mouth ulcers
- Yellow-tinged pale skin Nerve symptoms can appear before the anaemia and are the reason not to delay treatment.
Related symptoms
Related lab panels
When to discuss with a doctor
A low B12, especially with a macrocytic anaemia or nerve symptoms such as tingling, numbness or balance problems, should prompt a search for the cause — and pernicious anaemia is confirmed with intrinsic factor antibodies. It matters to identify because the treatment differs: since absorption is the problem, it is usually given as B12 injections (initially frequent, then maintenance for life), not tablets. Starting treatment promptly is important because delayed nerve damage can become permanent. Because it is autoimmune, associated conditions (especially thyroid) are checked. Mediora.AI shows the B12, MMA and red-cell pattern that points toward B12 deficiency; the diagnosis and treatment plan belong with your doctor.