Macrocytic anaemia is a blood condition in which red blood cells prove inefficient for oxygen transport. The most common forms are megaloblastic and pernicious anaemia. Around 2 to 4% of the global population is affected by macrocytosis, and 60% of them have anaemia. 

Due to little to no absorption of vitamin B12, individuals can develop pernicious anaemia, and this is often accompanied by autoimmune conditions. Understanding its causes, recognising its symptoms, and seeking timely treatment is important for the effective management of macrocytic anaemia. 

This guide explains macrocytic anaemia, its causes, symptoms, diagnosis, and treatment, as well as the differences between megaloblastic anaemia and pernicious anaemia.

What is Macrocytic Anaemia?

Macrocytic anaemia is a condition in which abnormally large red blood cells (RBCs) are present in the bloodstream. Enlarged RBCs do not work properly, severely reducing oxygen-carrying ability and causing several other health complications.

Among the most common types of macrocytic anaemia, megaloblastic anaemia results from impaired DNA synthesis. Pernicious anaemia is another well-known subtype, which is a particular kind of anaemia owing to vitamin B12 deficiency from poor absorption.

Causes of Macrocytic Anaemia

The main primary causes of macrocytic anaemia  include:

• Vitamin B12 deficiency – Often due to poor dietary intake or absorption issues.
• Folate deficiency – Common in individuals with malabsorption disorders, excessive alcohol consumption, or poor diet.

Pernicious anaemia is caused by the autoimmune destruction of parietal gastric cells, which results in intrinsic factor deficiency. This deficiency results in malabsorption of vitamin B12, which is dependent on intrinsic factors for uptake from the gut.

• Liver disease – It affects RBC production and produces macrocytosis.
• Hypothyroidism – Can disrupt normal RBC formation.
• Bone marrow disorders – Macrocytosis can develop from conditions such as myelodysplastic syndrome.
• Certain medications – Drugs such as methotrexate, zidovudine, and chemotherapy agents can impair DNA synthesis.

Symptoms of Macrocytic Anemia

Common macrocytic anaemia symptoms include:

• Fatigue and weakness
• Shortness of breath
• Pale or jaundiced skin
• Glossitis (inflamed tongue)
• Numbness or tingling in the hands and feet.
• Difficulty concentrating or memory problems
• Irregular heartbeat

Diagnosis of Macrocytic Anemia

Healthcare providers generally diagnose macrocytic anaemia by the following:

• Complete Blood Count (CBC) – RBC size (MCV) and haemoglobin are determined.
• Peripheral Blood Smear – It identifies enlarged RBCs and any abnormalities.
• Serum Vitamin B12 and Folate Tests – Checks for deficiencies causing anaemia.
• Intrinsic Factor Antibody Test – Used to diagnose pernicious anaemia.
• Bone Marrow Biopsy – Used in the cases of suspected bone marrow disorders.

Treatment Options for Macrocytic Anemia

The treatment of macrocytic anaemia depends upon its respective cause:

• Vitamin B12 Supplementation – Orally and through injections for pernicious anaemia or dietary deficiencies.
• Folate Supplementation – For individuals with folate deficiency.
• Managing underlying Conditions – To treat liver disease, hypothyroidism or bone marrow disorder.
• Adjusting Medications – Alternative medications may be considered if there is suspicion of drug-induced macrocytic anaemia.
• Dietary Changes – Increasing intake of vitamin B12 and folate-rich foods like fish, meat, eggs, dairy, leafy greens, fortified cereals, and grains.

Difference Between Megaloblastic Anemia and Pernicious Anemia

Here is a table describing the differences between megaloblastic anaemia and pernicious anaemia:

Feature	Megaloblastic Anemia	Pernicious Anemia
Definition	Vitamin B12 deficiency, with the lack of intrinsic factors can cause this specific type of macrocytic anaemia.	Vitamin B12 deficiency, with the lack of intrinsic factors can cause this specific type of macrocytic anaemia.
Cause	Vitamin B12 or folate deficiency.	Intrinsic factor deficiency results from the autoimmune destruction of gastric parietal cells.
Diagnosis	Large RBCs are seen on blood tests, and a vitamin B12 or folate deficiency.	Positive intrinsic factor antibody test, low vitamin B12 levels.
Treatment	Deficiency regarding vitamin B12 or folate supplementation.	Lifelong vitamin B12 injections or high-dose oral therapy.

FAQs about Macrocytic Anemia

1. What is the difference between macrocytic anaemia and pernicious anaemia?

Macrocytic anaemia is the term for anaemia associated with large RBCs, whereas pernicious anaemia is a specific macrocytic anaemia associated with vitamin B12 malabsorption secondary to intrinsic factor deficiency.

2. How is pernicious anaemia treated?

Treatment requires a lifelong supply of vitamin B12, most commonly given by injection or in high doses by mouth.

3. Can macrocytic anaemia be prevented?

Yes, a balanced diet for vitamin B12 and folate, treatment or management of other underlying conditions, and avoidance of alcohol overdosing can help prevent macrocytic anaemia.

4. Is macrocytic anemia serious?

If left untreated, macrocytic anaemia may become complicated with neurological damage (especially in pernicious anaemia), heart issues, and severe fatigue.

5. Can macrocytic anaemia be reversed?

Yes, if the underlying cause is addressed early. Vitamin B12 or folate supplementation can correct deficiencies, and treating conditions like hypothyroidism or liver disease can help reverse macrocytic anaemia in many cases.

6. What foods should I eat to prevent macrocytic anaemia?

To prevent macrocytic anaemia, include foods rich in vitamin B12 and folate, such as lean meats, fish, eggs, dairy products, leafy greens, beans, and fortified cereals.

7. Can macrocytic anaemia be a sign of an underlying serious condition?

Yes, macrocytic anaemia can indicate serious health issues such as liver disease, hypothyroidism, or bone marrow disorders like myelodysplastic syndrome. A proper medical evaluation is essential to determine the underlying cause.

8. How long does it take to recover from macrocytic anaemia with treatment?

Recovery depends on the cause and severity. For vitamin B12 or folate deficiency, symptoms may improve within a few weeks of supplementation, but neurological symptoms in pernicious anaemia may take longer and may not fully reverse if untreated for an extended period.

Conclusion

Proper diagnosis and management of macrocytic anaemia will prevent long-term complications. If you suspect you have symptoms of macrocytic anaemia, consult a healthcare professional promptly. At DocTutorials, we address a variety of other healthcare subjects and provide top-notch video lectures, expert advice, mock examinations, and additional resources for aspiring medical students. For more NEET PG exam preparation resources and in-depth learning, visit DocTutorials today!