Megaloblastic anemia is a condition that causes unusually large red blood cells. Red blood cells carry oxygen to the tissues and organs in the body. Abnormalities in the red blood cells interfere with oxygen delivery.
This article explores megaloblastic anemia, including its symptoms, causes, and treatment.
Megaloblastic anemia is a blood condition that causes a person to have atypical red blood cells.
The red blood cells become misshapen and unusually large (megaloblasts), and the bone marrow makes fewer of them. Additionally, the red blood cells do not mature as usual or function properly.
The hemoglobin in red blood cells carries oxygen to organs and tissues throughout the body. A person with megaloblastic anemia has fewer red blood cells that can carry oxygen to the organs and tissues.
Megaloblastic anemia is only one form of anemia — other forms exist as well. Megaloblastic anemia is not rare, but doctors do not know its exact prevalence because of insufficient research.
A 2018 cross-sectional study involving 1,150 people with anemia found that megaloblastic anemia occurred in 3.6% of the cases of anemia.
A deficiency in vitamin B12 or vitamin B6 (folate) is the most common cause of megaloblastic anemia. Both vitamins play a role in the development of healthy red blood cells. When the body does not have enough of these vitamins, red blood cells may not develop as usual.
Less often, an inherited genetic condition that affects the body’s ability to absorb some vitamins can lead to megaloblastic anemia. For instance, congenital folate malabsorption syndrome occurs in some infants.
Megaloblastic anemia can also occur as a side effect of certain medications that affect bone marrow function.
What causes vitamin B12 deficiency?
- Autoimmune conditions: Pernicious anemia is an autoimmune condition that affects a person’s ability to absorb vitamin B12.
- Digestive conditions: The small intestine absorbs nutrients from the foods a person eats. A digestive condition that damages the small intestine, such as celiac disease, can lead to a vitamin B12 deficiency.
- Diet: Although the liver stores excess vitamin B12, someone who eats very few foods containing vitamin B12 can develop a deficiency over time.
The symptoms of megaloblastic anemia may develop slowly. Someone may not have symptoms for years. Eventually, the lack of red blood cells affects the amount of oxygenated blood that various body parts receive.
A wide variety of symptoms can develop, including:
- Diet: Individuals who do not eat meat, eggs, or dairy may have an increased risk of megaloblastic anemia due to a lack of vitamin B12. A
2014 reviewreported an 80% prevalence of vitamin B12 deficiency in populations in India and Hong Kong, where vegans do not often eat B12-fortified foods or use supplements.
- Medications: Certain medications, such as metformin and proton pump inhibitors, may limit the absorption of B12.
- Certain medical conditions:
Health conditionssuch as celiac disease, ulcerative colitis, and Crohn’s disease may interfere with absorption of vitamin B12.
Healthcare professionals diagnose megaloblastic anemia using medical history, physical exams, and blood tests.
A medical history helps establish a person’s risk factors and symptoms. A physical exam may also help rule out other conditions.
- Complete blood count: This test provides information on the red blood cell count, white blood cells, and platelets.
- Peripheral blood smear: This involves looking under a microscope to see the shape and size of the red blood cells.
- Reticulocyte count: This blood test checks for immature red blood cells in the bone marrow.
Blood tests can also confirm a vitamin B12 or folate deficiency.
Healthcare professionals typically recommend taking supplements if a vitamin deficiency is causing megaloblastic anemia.
For adults, doctors may recommend a daily oral dose of
Doctors will also treat any underlying conditions that may contribute to megaloblastic anemia, such as Crohn’s disease.
The best way to prevent megaloblastic anemia is to eat enough foods that contain vitamin B12 and folate to avoid a deficiency.
Individuals who follow a strict vegan diet may want to consult their doctor about taking supplements.
Foods with vitamin B12
Although vitamin B12 supplements are available, several foods contain this vitamin. Animal products such as the following are the
In addition to meat, eggs, and dairy products, some fortified cereals and nutritional yeast contain vitamin B12.
Pernicious anemia is a form of megaloblastic anemia. Pernicious anemia involves an autoimmune disease that interferes with the absorption of vitamin B12.
According to the
Typically, the body produces a protein called intrinsic factor that helps with vitamin B12 absorption. People with pernicious anemia produce an antibody that prevents the effects of intrinsic factor. This inhibits the body’s ability to absorb vitamin B12, leading to megaloblastic anemia.
It is helpful to consult a doctor any time someone has symptoms of anemia, such as fatigue, pale skin, and shortness of breath.
People who eat a vegan diet should also seek advice from a healthcare professional to ensure that they consume enough vitamin B12.
The outlook for people with megaloblastic anemia is
With timely treatment, the condition is usually not fatal.
Megaloblastic anemia causes the body to produce unusually larger and fewer red blood cells. This affects the red blood cells’ ability to transport oxygen to the organs and tissues in the body.
The most frequent cause is a deficiency in vitamin B12 or folate. Treatment with vitamin supplements usually helps improve symptoms and resolve the condition.