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What Is Pernicious Anemia?

Dr. Omer Hassan Aftab Ahmed

2 min read

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According to Gastroenterologists  anemia occurs when there is a severe deficiency of red blood cells (RBCs) resulting in chronic fatigue and weakness. In the case of pernicious anemia, this lack of red blood cells is due to a vitamin B12 deficiency; that is, the body is unable to fully absorb the vitamin from food.

B12 deficiency anemia was often fatal in the past, hence the name ‘pernicious’, meaning ‘deadly’.

Difference Between B12 Deficiency and Pernicious Anemia:

A B12 deficiency is generally due to a poor diet, and can easily be reversed after B12 levels are stabilized through dietary additions and supplementation. However, pernicious anemia is an autoimmune disorder that results from poor B12 absorption. The body cannot absorb the vitamin despite adequate intake of vitamin-rich foods. Pernicious anemia can also be genetic and permanent.


Pernicious anemia progresses slowly, which is why most people often become used to the symptoms, making them difficult to identify, in order to get a confirmed diagnosis visit an internal medicine specialist in Karachi:

  1. General:
  • Dizziness
  • Chest pain
  • Headaches
  • Shortness of breath
  • Cold hands and feet
  • Pale or yellowish skin
  • Unexplained weight loss
  1. Neural:
  • Irritability
  • Confusion
  • Depression
  • Unsteady gait
  • Balance issues
  • Dementia/memory loss
  • Hallucinations or delusions
  • Spasticity (stiff and tight muscles)
  • Nerve damage resulting in tingling and numbness in the hands and feet, muscle weakness, reduced reflexes, and sight issues due to
  1. Digestive:
  • Nausea
  • Vomiting
  • Heartburn
  • Weight loss
  • Loss of appetite
  • Bloating and gas
  • Constipation or diarrhea
  1. Cardiac:
  • Arrythmia (irregular heartbeat)
  • Heart murmur (a recurring sound in a stethoscope indicating a heart disease)
  • Heart enlargement
  • Cardiac failure
  1. Other:
  • Bleeding gums
  • Smooth, thick, red tongue
  • Poor reflexes, unusual movements (e.g. facial tremors), trouble feeding, and irritability in infants.


1-Lack of Intrinsic Factor(IF):

The main causative factor behind pernicious anemia, IF is a protein that aids vitamin B12 absorption in the small intestine by binding to it. In some cases, however, the immune system mistakenly attacks and damages the IF-producing parietal cells in the stomach, causing a halt in IF production. As a result, the consumed B12 is unable to be utilized and passes unabsorbed through the small intestine, leading to a vitamin B12 deficiency over time.

Surgical removal of part or all of the stomach also reduces the number of parietal cells, hence causing an IF deficiency. In rare cases, the natural inability to manufacture IF can be inherited from parents, resulting in a condition known as ‘Congenital (at birth) Pernicious Anemia’.

2-Malabsorption in the Small Intestine:

Pernicious anemia may also occur if the small intestine is unable to properly absorb vitamin B12. This malabsorption may be due to one or more of the following reasons:

  • Excess harmful bacteria in the small intestine, which use up the consumed vitamin B12 before it can be absorbed.
  • Celiac disease, Crohn’s disease, HIV, and other gastric conditions
  • Certain medicines like antacids, antibiotics, or type 2 diabetes medication that promote harmful bacterial growth. Proton Pump Inhibitors (PPIs) used for treating indigestion can also prevent the release of B12 from food by blocking stomach acid production.
  • A tapeworm infection (usually contracted from eating undercooked fish), which feeds off vitamin B12.
  • Surgical removal of part or all of the small intestine.


Red blood cells, or RBCs, need to reduce in size by dividing in order to exit the bone marrow where they are made, and travel throughout the body to transport oxygen. However, with a B12 deficiency, these cells are unable to divide properly and remain large (macrocytes); hence decreasing the number of oxygen-carrying RBCs in the bloodstream.

Moreover, the production is reduced due to their high concentration in the bone marrow, and even they die off prematurely. This is why pernicious anemia is also sometimes called ‘Megaloblastic Anemia’ due to abnormally large RBCs.

Risk Factors:

While older people are at higher risk of developing pernicious anemia due to reduced stomach acid and IF production, other risk factors include:

  • An autoimmune disease involving the endocrine glands, like type 1 diabetes, Grave’s Disease, or vitiligo.
  • Certain intestinal conditions like Crohn’s disease, HIV, and intestinal infections.
  • Partial or complete stomach and/or small intestine removal
  • A strict vegetarian or vegan diet without B12 supplements.
  • Breastfed infants of strict vegan or vegetarian mothers.
  • A family history of pernicious anemia
  • Alcohol abuse.

While pernicious anemia is easily treatable, it can cause serious, even fatal complications if left untreated for over 6 months. So, contact your doctor immediately if you observe any of the above symptoms for an accurate diagnosis and prompt treatment.

You can also book an appointment with a top Gastroenterologist in Lahore, Karachi and Islamabad through oladoc.com, or call our helpline at 042-3890-0939 for assistance to find the RIGHT Doctor for your gut-related concerns.

Disclaimer: The contents of this article are intended to raise awareness about common health issues and should not be viewed as sound medical advice for your specific condition. You should always consult with a licensed medical practitioner prior to following any suggestions outlined in this article or adopting any treatment protocol based on the contents of this article.

Dr. Omer Hassan Aftab Ahmed
Dr. Omer Hassan Aftab Ahmed - Author Dr. Omer Hassan Aftab Ahmed is among the Best Gastroenterologists in Islamabad. Dr. Omer Hassan Aftab Ahmed is a Gastroenterologist practicing in Islamabad. Dr. Omer Hassan Aftab Ahmed has the following degree: M.B.B.S and has 9 years of experience. You can book an appoitment with him through oladoc.
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