Warm autoimmune hemolytic anemia (wAIHA) is the most common form of autoimmune hemolytic anemia, accounting for approximately 60–75% of cases. It occurs when the immune system mistakenly produces antibodies, primarily immunoglobulin G (IgG), that bind to healthy red blood cells and mark them for premature destruction. The condition is termed “warm” because these antibodies are most active at normal body temperature (37°C), unlike the antibodies involved in certain other forms of autoimmune hemolytic anemia that react more strongly at lower temperatures. Red blood cell destruction, known as hemolysis, occurs primarily in the spleen and liver (extravascular hemolysis). In approximately 30–50% of cases, activation of the complement system also contributes to this process. Normally, red blood cells circulate for about 120 days before being removed from the bloodstream. In wAIHA, their accelerated destruction exceeds the bone marrow’s ability to replace them, resulting in anemia and reduced oxygen delivery to tissues. 1-3
The estimated incidence of warm AIHA is roughly 0.5–2.3 cases per 100,000 people per year. The condition can occur at any age, but the median age at diagnosis is 52 years, and the risk rises sharply in older adults, up to 10 times higher in people aged 75 or older compared to those under 50. Women are slightly more likely to be affected than men. 2, 4, 5
About half of all cases have no identifiable cause and are called primary (or idiopathic) warm AIHA. The other half are secondary, meaning they are linked to another condition such as a blood cancer (lymphoproliferative disorder), an autoimmune disease, an immune deficiency, an infection, or a medication. 1, 3
Symptoms range from mild fatigue, shortness of breath, and a rapid heartbeat to, in severe cases, chest pain, confusion, and dark urine. Yellowing of the skin (jaundice) and an enlarged spleen may also occur. 2, 5
Effective treatments are available. Corticosteroids are the standard first-line therapy, and medications such as rituximab, immunosuppressants, and other agents are used when additional treatment is needed. 1, 3, 5
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