The main difference between megaloblastic and pernicious anemia is that megaloblastic anemia occurs when the intestine cannot absorb vitamin B12 or folic acid, whereas pernicious anemia occurs due to vitamin B12 deficiency.
Megaloblastic anemia and pernicious anemia are two types of macrocytic anemia that occur due to low levels of vitamin B12 in the body. Pernicious anemia is a type of megaloblastic anemia.
Key Areas Covered
1. What is Megaloblastic Anemia
– Definition, Causes, Signs and symptoms, Diagnosis and Treatment
2. What is Pernicious Anemia
– Definition, Causes, Signs and symptoms, Diagnosis and Treatment
3. Similarities – Megaloblastic and Pernicious Anemia
– Outline of Common Features
4. Difference Between Megaloblastic and Pernicious Anemia
– Comparison of Key Differences
Key Terms
Megaloblastic Anemia, Pernicious Anemia
What is Megaloblastic Anemia
Megaloblastic anemia is a type of macrocytic anemia that occurs due to the inability of the intestine to absorb vitamin B12. The main characteristic feature of megaloblastic anemia is the presence of large red blood cell precursors called megaloblasts in the bone marrow. It occurs due to impaired DNA synthesis that inhibits nuclear division. However, cytoplasmic maturation that is dependent on RNA and protein synthesis is not impaired. This causes asynchronous maturation between the nucleus and the cytoplasm.
Compared to other types of anemia, megaloblastic anemia usually has a slow onset and rapid progression. As far as the major cause for this condition is concerned, the characteristic defect in red cell DNA synthesis is mostly due to hypovitaminosis, especially as a result of vitamin B12 and folic acid deficiency. However, Vitamin B12 deficiency alone will not be able to produce the signs of the syndrome if there is a sufficient amount of folate. Therefore, folic acid supplementation in the absence of vitamin B12 can often prevent megaloblastic anemia.
Major causes for the deficiency of Vitamin B12:
- Reduced dietary intake
- Malabsorption due to conditions like achlorhydria
- Coeliac disease
- Intrinsic factor deficiency, which is essential for the absorption of vitamin B12
- Chronic pancreatitis
- Ileal resection and anastomosis
Major causes for Folic acid deficiency:
- Chronic alcoholism
- Reduced intake
- Increased demand- pregnancy, infancy
- Congenital or drug-induced malabsorption
- Jejunal resection
- Inherited DNA synthesis disorders
In addition, deficiency of micronutrients like copper is also known to be a well-known reason for this condition to develop.
Patients with this condition will experience general features of anemia, such as shortness of breath, chest pain, palpitation, fatigue, and malaise. There will also be signs like glossitis and a smooth tongue appearance.
Diagnosis and Treatment
A full blood count in suspected patients will reveal reduced hemoglobin levels with an increased MCV count, revealing a macrocytosis. A peripheral blood smear will further confirm the diagnosis with the presence of hypersegmented neutrophils, anisocytosis, and poikilocytosis.
Moreover, a biochemical analysis will show an increased lactic acid dehydrogenase (LDH) level (typical of serum and hematopoietic cells), raised levels of homocysteine and methylmalonic (Vitamin B12 deficiency), and homocysteine (folate deficiency).
The treatment will be based on the etiology, which will have to be addressed individually. If there is a reduction of intake, dietary or supplementary intake should be encouraged.
What is Pernicious Anemia (PA)
Pernicious anemia is a type of megaloblastic anemia that occurs due to the deficiency of vitamin B12 secondary to malabsorption as a result of intrinsic factor deficiency, a compound secreted by the inner mucosal lining of the intestines.
This may occur due to various underlying conditions such as autoimmunity and drugs. The commonest complication with untreated PA is the impairment of neurological functions since Vitamin B12 is a compulsory factor needed for the development of neurons.
Therefore, the most usual signs and symptoms of this condition include tingling sensation and numbness in the hands and feet, malaise, fatigue, and bright red smooth tongue.
Diagnosis and Treatment
Patients with clinical signs and symptoms suggestive of PA can be diagnosed with a full blood count, which will show low hemoglobin, high MCV, and normal MCHC, suggestive of macrocytic anemia.
A peripheral blood smear can be done next, which will often show large, fragile, immature erythrocytes, known as megaloblasts, Ovalocytes, and hypersegmented neutrophils (common to all megaloblastic anemia). Reduced Serum B12 levels will further confirm the diagnosis.
Treatment for PA usually depends on the underlying etiology, and neurological impairments should be addressed promptly to prevent severe complications.
A high dose of Vitamin B 12, given orally, has been found to be effective in most patients, but some will only respond to intramuscular injections containing cyanocobalamin, which is the treatment of choice for PA.
Similarities Between Megaloblastic and Pernicious Anemia
- Megaloblastic anemia and pernicious anemia occur due to the deficiency of vitamin B12 in the body.
- Very large red blood cells occur in both types of anemia, reduced in number.
Difference Between Megaloblastic and Pernicious Anemia
Definition
Megaloblastic anemia refers to a type of macrocytic anemia, a type of anemia characterized by very large red blood cells. In contrast, pernicious anemia refers to a relatively rare autoimmune disorder that causes diminishment in dietary vitamin B12 (cobalamin) absorption, resulting in B12 deficiency and subsequent megaloblastic anemia.
Type
Megaloblastic anemia is a type of macrocytic anemia that produce large red blood cells, while pernicious anemia is a type of megaloblastic anemia.
Occurrence
While megaloblastic anemia occurs due to the inability of the intestine to absorb vitamin B12 or folate, pernicious anemia occurs due to vitamin B12 deficiency.
Signs and Symptoms
The signs and symptoms of megaloblastic anemia include shortness of breath, chest pain, palpitation, fatigue, and malaise, while the signs and symptoms of pernicious anemia include tingling sensation and numbness in the hands and feet, malaise, fatigue, and bright red smooth tongue.
Diagnosis
Both will show hypersegmented neutrophils on the peripheral blood smear, but PA will characteristically reveal ovalocytes.
Conclusion
Megaloblastic and pernicious anemia are two types of macrocytic anemia that produce large red blood cells. Megaloblastic anemia is a type of macrocytic anemia that occurs due to the inability to absorb vitamin B12 and folic acid by the intestine. In comparison, pernicious anemia is a form of megaloblastic anemia that occurs due to the deficiency of vitamin B12. The main difference between megaloblastic and pernicious anemia is their cause.
Reference:
1. Hariz A, Bhattacharya PT. Megaloblastic Anemia. [Updated 2023 Apr 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing.
2. Vaqar S, Shackelford K. Pernicious Anemia. [Updated 2023 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing.
Image Courtesy:
1. “Hypersegmented neutrophil” (Public Domain) via Commons Wikimedia
2. “Hydroxocobalamin Injection” By Sbharris – Own work (CC BY-SA 3.0) via Commons Wikimedia
