Autoimmune hemolytic anemia (AIHA) is a blood disorder that occurs when your immune system mistakenly attacks your own red blood cells. Red blood cells are responsible for carrying oxygen throughout the body. When antibodies destroy red blood cells faster than the body can replace them, tissues do not receive enough oxygen. This leads to symptoms such as fatigue, weakness, and headaches.

AIHA is rare, affecting one to three people per 100,000 each year. The exact cause is often unknown, though infections, medications, or underlying autoimmune conditions can trigger the disorder. Treatment usually involves medications to suppress the immune system and, in severe cases, blood transfusions to restore red blood cell levels.

Types Of Autoimmune Hemolytic Anemia

There are two main types of AIHA, classified based on the temperature at which the immune system attacks red blood cells. This distinction matters because treatment approaches differ.

Warm Autoimmune Hemolytic Anemia
This is the most common type, making up about 70–80% of adult cases and half of pediatric cases. Antibodies attack red blood cells at normal body temperature, causing anemia.

Cold Autoimmune Hemolytic Anemia
Also called cold agglutinin disease (CAD), this type usually affects adults aged 40–80. Here, antibodies activate in cooler temperatures, causing red blood cells to clump and break down after cold exposure.

Primary And Secondary AIHA

  • Primary AIHA: About half of cases are idiopathic, meaning no clear cause.

  • Secondary AIHA: Caused by another condition such as autoimmune disease, infection, cancer, or medication.

Symptoms Of Autoimmune Hemolytic Anemia

Symptoms vary depending on severity. Since red blood cells carry hemoglobin to deliver oxygen, a shortage reduces oxygen supply throughout the body.

Common symptoms include:

  • Fatigue

  • Weakness

  • Rapid heart rate

  • Headaches

  • Brain fog or poor concentration

As anemia progresses, new symptoms may develop:

  • Pale skin

  • Dizziness

  • Sore tongue

  • Shortness of breath

  • Dark urine

  • Enlarged spleen with abdominal pain

Severe, untreated AIHA may cause:

  • Fever

  • Chest pain

  • Fainting

  • Jaundice

  • Liver or heart failure

Causes Of Autoimmune Hemolytic Anemia

Normally, the immune system protects against infections. In AIHA, it mistakenly marks red blood cells as harmful and creates antibodies to destroy them.

Red blood cells typically live around 120 days before being filtered out by the spleen. In AIHA, antibodies destroy them prematurely, leading to an insufficient red blood cell supply.

Triggers for secondary AIHA include:

  • Infections such as influenza, pneumonia, tuberculosis, and Epstein-Barr virus

  • Medications including NSAIDs, chemotherapy, antivirals, and some antibiotics

  • Autoimmune diseases such as lupus, Sjögren's syndrome, systemic sclerosis, and rheumatoid arthritis

  • Immunodeficiency after organ or bone marrow transplant

  • Certain cancers, including lymphoma, leukemia, ovarian, and prostate cancer

Risk Factors

While anyone can develop AIHA, some factors increase risk:

  • Age: Most common between 50–80 years old

  • Sex: Slightly more frequent in people assigned female at birth

  • Health status: Having autoimmune disease, blood cancer, or a weakened immune system

Diagnosis

Healthcare providers use medical history, physical exam, and blood tests to confirm AIHA and rule out other causes of anemia.

Diagnostic tests may include:

  • Complete blood count (CBC): Checks levels of blood cells and hemoglobin

  • Reticulocyte count: Measures young red blood cells to see if bone marrow is producing enough

  • Peripheral blood smear: Examines shape and size of red blood cells under a microscope

  • Coombs test: Detects antibodies attached to red blood cells or floating in the blood

  • Lactate dehydrogenase (LDH): High levels suggest cell breakdown

  • Haptoglobin: Low levels may indicate red blood cell destruction

  • Bilirubin test: Elevated levels can show increased breakdown of red blood cells

  • Agglutinins test: Detects antibodies that clump red blood cells, helping diagnose cold AIHA

Treatment

The main goal of treatment is to slow down or stop the immune system from destroying red blood cells.

Medications
Corticosteroids such as prednisone are the first-line treatment, suppressing the abnormal immune response. Most people improve within a few weeks. If symptoms persist, other medications like rituximab may be prescribed.

Splenectomy
Surgical removal of the spleen may be considered for severe or treatment-resistant warm AIHA, reducing red blood cell destruction.

Blood Transfusions
In severe cases, transfusions restore red blood cell levels and improve oxygen supply, though they may need to be repeated.

Lifestyle Adjustments

  • Avoid cold temperatures if you have cold AIHA

  • Take folic acid supplements to support red blood cell production

  • Follow your provider’s plan to prevent flares

Prevention

AIHA cannot always be prevented, but some steps may help manage symptoms and reduce flare-ups:

  • Treat and manage underlying autoimmune or health conditions

  • Reduce infection risk with good hygiene and vaccines

  • Dress warmly and avoid cold exposure if you have cold AIHA

Complications

If untreated, AIHA or its treatments can cause serious complications:

  • Splenomegaly (enlarged spleen), with risk of rupture

  • Infections, especially after immunosuppressants or splenectomy

  • Thrombosis (blood clots), raising risk of heart attack or pulmonary embolism

  • Skin ulcers or tissue damage in cold AIHA

  • Kidney dysfunction from breakdown products of destroyed red blood cells

A Quick Review

Autoimmune hemolytic anemia (AIHA) is a rare condition where the immune system destroys healthy red blood cells too early. This leads to anemia, causing fatigue, dizziness, and shortness of breath.

The exact cause is often unknown, but infections, medications, autoimmune diseases, and cancers can trigger it. Treatments include medications, surgery, and lifestyle changes that help manage symptoms and improve quality of life.