Different Types of Anemia and Their Causes

Iron-Deficiency Anemia

The most common form of anemia is iron-deficiency anemia (IDA). As the name suggests, low iron levels cause IDA. The body needs iron to make hemoglobin. Without enough iron, the body cannot make healthy RBCs, and this leads to anemia.

Healthy iron levels depend on dietary intake because the body cannot make its own iron. As a result, IDA is very common in people with low-iron diets. In addition to those at increased risk due to low intake, groups who are at the highest risk for IDA include:

Many of the groups at the highest risk for IDA have conditions that affect the GI tract. This commonality reflects how iron is absorbed by the body. Most of the iron consumed in the diet is absorbed in the duodenum and upper jejunum — the first two parts of the small intestine. As a result, conditions affecting the GI tract significantly increase the risk of reduced iron absorption and IDA.

Recognizing symptoms of IDA is essential for prompt treatment of anemia. Depending on the person and the cause of anemia, symptoms can appear suddenly or develop slowly. Symptoms of IDA, which are shared by many other types of anemia, include:

Importantly, people with mild anemia may have no symptoms. If you’re at higher risk for IDA, your doctor may recommend doing bloodwork to check for signs of anemia, regardless of whether you have symptoms.

Vitamin-Deficiency Anemia

Vitamin-deficiency anemia includes folate (vitamin B9) and cobalamin (vitamin B12) deficiencies. Along with iron, the body needs both folate and cobalamin to make healthy RBCs.

Cobalamin deficiency has three potential causes: low-cobalamin diet, autoimmune disease, and gastrointestinal (GI) tract disease. The primary dietary sources of cobalamin are meat, eggs, and milk. People with diets low in these foods are at risk of cobalamin deficiency and subsequent anemia.

Autoimmune disease refers to conditions where the immune system attacks the body’s own healthy cells. Sometimes, immune cells attack a substance called intrinsic factor — a protein made in the stomach that promotes the breakdown and absorption of cobalamin. Without intrinsic factor, people develop pernicious anemia — cobalamin deficiency caused by the autoimmune destruction of intrinsic factor.

People who’ve had surgery that removes part of the stomach or the end of the small intestine can also develop cobalamin deficiency and anemia because of reduced cobalamin absorption. Other conditions like Crohn’s disease and celiac disease can also disrupt cobalamin absorption, leading to deficiency and anemia.

Lack of folate in the diet causes most folate-deficiency anemias. The primary natural sources of folic acid are leafy vegetables, citrus fruits, whole grains, and beans. People with diets low in these foods can develop folate deficiency. Other causes include:

Cobalamin- and folate-deficiency anemia may cause symptoms similar to those caused by IDA, such as fatigue and pale skin. Other shared symptoms include:

Because of its role in nerve cell development, cobalamin deficiency can also cause neurological symptoms, including:

Sickle Cell Anemia

Sickle cell disease (SCD) causes sickle cell anemia. SCD is a lifelong illness. Due to an inherited genetic mutation (change in genes) that affects the shape of hemoglobin, RBCs take on a crescent or ‘sickle’ shape in people with SCD. Sickled RBCs break apart easily and die faster than normal RBCs. This leads to anemia.

Normal RBCs are flexible and disc-shaped and able to move smoothly through blood vessels. Sickled RBCs, on the other hand, cannot bend easily and get stuck. As a result, people with SCD are at an increased risk of stroke, blood clots in the legs, heart attacks, and other blood clotting complications.

SCD can also cause other serious complications. Acute chest syndrome (ACS), for example, is a complication specific (only occurs in this condition) to SCD and requires emergency medical treatment. ACS is caused by a lung infection and/or sickle cells blocking the lungs’ blood vessels. Symptoms include chest pain, trouble breathing, and fever.

Pulmonary hypertension — high blood pressure in the lungs — is another serious complication that mainly affects adults with SCD.

Other serious potential complications of SCD include:

As with other anemia types, symptoms of SCD can vary by individual and over time. Sickle cell anemia is one of the main signs of SCD and causes symptoms similar to other types of anemia, such as fatigue, shortness of breath, and pale skin. Other signs and symptoms of SCD include:

Thalassemia

Thalassemia is another inherited blood disorder that affects hemoglobin production. Without functional hemoglobin, RBCs cannot carry enough oxygen and anemia results.

Hemoglobin is made of four protein chains: two alpha chains and two beta chains. Four genes are responsible for making the alpha chains, and two genes are responsible for the beta chains. People inherit these genes from their parents. Based on how the condition affects these protein chains, thalassemia is divided into two categories: alpha thalassemia and beta thalassemia.

Thalassemia is also classified by severity. Severity is determined based on how many defective hemoglobin genes are present. For alpha thalassemia, the classifications are:

For beta thalassemia, the classifications are:

Thalassemia symptoms depend on the type of thalassemia. As mentioned, people with thalassemia trait have no symptoms. People with minor thalassemia will likely have minor anemia symptoms. Intermedia or major thalassemia can cause moderate symptoms, including:

Severe thalassemia symptoms, which can result from mild to moderate disease, include:

Symptoms of severe alpha thalassemia are usually present at birth, while those of severe beta thalassemia often develop by age 2. Thalassemia, especially more severe disease, can cause various complications. People with thalassemia can have issues due to having too much iron from frequent blood transfusions or their condition. Too much iron can damage the heart, liver, and endocrine (hormone) system.

Hemolytic Anemia

Another type of anemia is hemolytic anemia, which occurs when the body destroys RBCs faster than it can make new ones. Depending on its cause, hemolytic anemia symptoms may be mild or serious and evolve quickly or slowly over time.

The body gets rid of old or damaged RBCs in the spleen and other areas through hemolysis — the name given to the RBC destruction process. Normally, this process is balanced by the creation of new RBCs in the sponge-like center of bones, called bone marrow. Numerous conditions can lead to increased hemolysis and hemolytic anemia. Hemolytic anemia conditions can be inherited or acquired. Inherited (passed from parent to child) conditions causing hemolytic anemia include:

Acquired (develops during life and isn’t inherited) conditions that cause hemolytic anemia include:

As with other types of anemia, symptoms of hemolytic anemia vary by individual. Hemolytic anemia also shares symptoms with other anemia types. Possible symptoms include:

Aplastic Anemia

Aplastic anemia, also called bone marrow failure, is a rare blood disorder. When the bone marrow doesn’t function properly, it can’t make enough blood cells, including RBCs. Similar to hemolytic anemia, aplastic anemia can develop rapidly or slowly. Aplastic anemia can be severe or mild depending on its cause but is generally considered serious.

Exactly how aplastic anemia develops isn’t fully understood, but the most common known cause is autoimmune bone marrow destruction. As a result, autoimmune conditions, such as lupus, increase the risk of developing aplastic anemia. Other conditions that increase the risk of aplastic anemia include:

When aplastic anemia develops rapidly, people tend to notice immediate, severe symptoms. However, if the condition takes time to develop, symptoms may not be noticeable or mild. In either scenario, symptoms may include:

Anemia of Chronic Disease

Anemia of chronic disease (ACD) is anemia caused by inflammation due to chronic (long-lasting) medical conditions. Chronic inflammation affects the body’s ability to use its stored iron to make new RBCs, which leads to anemia.

ACD is often associated with autoimmune disease, but any chronic condition that causes inflammation can lead to ACD. These include:

Symptoms of ACD are similar to those of IDA, including fatigue, difficulty breathing, pale skin, headaches, dizziness, and sweatiness.

Talk With Your Doctor

Because of symptom overlap between types of anemia, telling them apart requires a thorough evaluation by a healthcare professional. If you have any of these signs or symptoms or are living with anemia, it’s important to discuss your symptoms or condition with your doctor. Your doctor will review your medical history and perform testing to diagnose the type of anemia you have and determine the best treatment plan.