What Is Microcytic Anemia?

Microcytic anemia is a blood disorder in which the red blood cells are too small due to a lack of hemoglobin.

Hemoglobin, an iron-rich protein, binds to oxygen, delivering it throughout the body. With microcytic anemia, smaller red blood cells carry less oxygen, which leads to low energy and fatigue. 

Microcytic anemia may develop due to insufficient dietary iron, blood loss, or other medical problems. It is often found during routine blood work. Iron supplements may help to treat it, but identifying and managing the underlying cause is crucial.

This article explains the symptoms and causes of microcytic anemia and how it is treated and monitored.

Signs and Symptoms of Microcytic Anemia 

The symptoms of microcytic anemia develop over time. It often does not have any signs during the early stages.

Symptoms tend to be vague, not specifically unique to anemia, and can include:

• Fatigue, low energy, sleepiness, and sluggishness 
• General weakness 
• Pale skin 
• Dizziness 
• Headaches 
• Irritability 
• Difficulty concentrating 
• Enlargement of the spleen, which may make the abdomen appear larger

You can have all or some of these symptoms with varying levels of severity. People with underlying medical conditions may have more severe anemia. More severe anemia tends to cause more severe symptoms.

Types and Causes of Microcytic Anemia

Microcytic anemia occurs when the body cannot make red blood cells of normal size. This can happen if you are deficient in certain components of the red blood cells or it can occur due to illnesses that prevent proper red blood cell development.

There are several types of microcytic anemia with different causes that make it difficult for the body to produce healthy red blood cells.

Hypochromic Microcytic Anemia

This most common type of microcytic anemia; "hypochromic" means the cells are pale in color. Iron and hemoglobin are red. When red blood cells are pale, it often means they do not have enough iron.

Common causes of hypochromic microcytic anemia include:

• Iron deficiency: When iron levels are low, red blood cells don’t develop properly. This can be due to not eating enough iron-rich food (meat, fish, beans, leafy green vegetables, and chicken), difficulty absorbing iron in your digestive tract, or blood loss. In premenopausal women, heavy menstrual periods are a common cause of iron-deficient anemia. 
• Sideroblastic anemia: Sideroblastic anemia interferes with how the body uses iron to make red blood cells. It is characterized by sideroblasts in the bone marrow, which are a type of premature red blood cell. Sideroblastic anemia can be acquired, and there are hereditary forms as well. It occurs due to dysfunction in how the body uses iron to make hemoglobin.
• Thalassemia: Thalassemia causes a defect in the production of hemoglobin. This hereditary condition is a genetic defect that affects the formation of hemoglobin, a component of the red blood cells. 

Normochromic Microcytic Anemias

In normochromic microcytic anemias, the red blood cells are small but the appropriate color. This can indicate a normal amount of iron and hemoglobin.

This type of anemia is often due to anemias to chronic inflammation, infection, or diseases that prevent red blood cells from developing properly. This can include:

• Autoimmune diseases, such as rheumatoid arthritis
• Cancer
• Crohn’s disease
• Diabetes
• Endocarditis
• HIV/Aids
• Kidney disease
• Tuberculosis

These chronic diseases can cause hemolysis and may also interfere with red blood cell production and iron metabolism. These illnesses can make it difficult for the body to produce red blood cells, resulting in microcytic anemia or normocytic (normal-size red blood cells) anemia.

Hyperchromic Microcytic Anemias

Red blood cells that are smaller than normal but have a darker hue are known as hyperchromic microcytic anemia.

Though rare, it is usually due to congenital spherocytic anemia, a genetic condition that causes a defect in the red blood cell membrane. As a result, red blood cells are darker, shaped like spheres, and break down faster.

Other Causes

Other causes of microcytic anemia include:

• Copper deficiency
• Excessive alcohol or illegal drug use
• Lead poisoning
• Side effects of medications
• Zinc excess, which causes copper deficiency

Sometimes these types overlap, or you can have more than one type of microcytic anemia. For example, lead toxicity can cause sideroblastic anemia. 

How Microcytic Anemia Is Diagnosed 

Microcytic anemia can cause signs that are detected on a physical examination, but it doesn’t always do so. Microcytic anemia is diagnosed with blood tests. Sometimes, additional specific blood tests are used to determine the cause. 

Mycrocytic anemia is sometimes detected during examinations and testing for other conditions or during a routine physical. Your healthcare provider may notice signs such as pale skin, a weak pulse, low blood pressure, a rapid heart rate, or splenomegaly (enlarged spleen).

Often, a complete blood count (CBC) is part of a routine medical checkup, and it is frequently ordered if there are any signs or symptoms of anemia. Other blood tests that you might need for further evaluation of microcytic anemia include a blood smear, iron tests, genetic tests, or tests for lead levels. Additional diagnostic tests are sometimes needed.

Blood tests include:

• CBC: With microcytic anemia, you may have a normal or low red blood cell count, a low mean corpuscular volume (MCV) that is below 80–100 femtoliters, red cell distribution width (RDW) that is normal or high, and a mean corpuscular hemoglobin concentration (MCHC) that's below 27–31 picograms per cell.
• Blood smear: With microcytic anemia, the red blood cells will appear small and often pale when observed through a microscope.
• Genetic tests: Genetic tests can identify thalassemia or hereditary causes of sideroblastic anemia.
• Iron levels: Iron levels can be measured in the blood to determine whether there is a deficiency.
• Lead levels: If there is a concern about lead toxicity, this toxic metal can be measured in a blood sample.

Other Diagnostic Tests 

Sometimes microcytic anemia is caused by bleeding or chronic disease. Your doctor may order additional diagnostic tests to identify the cause of your anemia. 

Tests you might need include:

• Urinalysis: This is testing a sample of urine. It can identify blood in the urine, which is one sign of hemolysis or bleeding.
• Imaging tests: If there is concern about cancer or a structural cause of bleeding, an imaging test such as ultrasound can help visualize it.
• Colonoscopy: This invasive test can identify sources of bleeding in the intestines.
• Endoscopy: This invasive test can identify bleeding, cancer, or ulcers in the esophagus or the stomach.
• Bone marrow biopsy: A bone marrow biopsy may be needed if there is concern about bone marrow disease or bone marrow cancer. A needle is used to take marrow from a bone to be examined in a lab.

Your medical history, family history, symptoms, physical examination, and blood tests would be used to determine which, if any, diagnostic test you might need. 

What Are the Treatments for Microcytic Anemia? 

There are many different treatments for microcytic anemia. Some treatments help resolve the symptoms, and others help your body produce normal red blood cells. 

A blood transfusion may be necessary to alleviate the effects of severe anemia. This can resolve your anemia if it developed due to an acute event, such as blood loss from trauma or surgery. For chronic conditions, repeat blood transfusions may be needed. 

Other treatments are focused on alleviating the cause of the anemia. 

Examples of treatments include:

• Surgical repair of a bleeding wound
• Iron replacement through supplements
• Treatment of an underlying illness, such as cancer 
• Treatment of lead toxicity 
• Management of thalassemia to avoid complications of the condition

Outlook for Microcytic Anemia

Microcytic anemia can improve with treatment. It may take weeks or months for you to feel better and for your blood tests to show improvement. Depending on the cause, you may need to continue long-term treatment to prevent microcytic anemia from recurring.

For example, if you have a problem absorbing iron from your diet, you may need to continue taking supplements to avoid becoming anemic again. And if you have thalassemia, you would need a long-term treatment regimen.

Living with microcytic anemia can be challenging. The fatigue and low energy of anemia can make it difficult to complete your daily tasks. It can also make exercise more difficult and lead to weight gain.

Summary 

Microcytic anemia describes a condition in which the red blood cells are small. This can occur due to several causes, including nutritional deficiency, hereditary conditions, acute or chronic bleeding, or chronic disease. Microcytic anemia causes nonspecific symptoms. The diagnosis relies on blood tests.

Assessment of the cause is critical because the cause guides treatment. Usually, treatment can normalize the red blood cells and alleviate symptoms, but sometimes treatment needs to be maintained long-term.