Autoimmune hemolytic anemia

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Autoimmune hemolytic anemia

Hematological system

Coagulation disorders


Vitamin K deficiency

Leukemoid reaction

Leukemoid reaction


Autoimmune hemolytic anemia

USMLE® Step 1 questions

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High Yield Notes

13 pages


USMLE® Step 1 style questions USMLE

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A 70-year-old man comes to the emergency department due to a syncopal episode that he experienced while playing with his grandchildren. He reports new exercise intolerance over the past few months, noting that he now cannot reach the mailbox without experiencing chest pain and shortness of breath. He also notes that his urine appears darker than normal. His past medical history is significant for hypertension and gastroesophageal reflux disease. He denies alcohol or tobacco use. His temperature is 37°C (98.6°F), pulse is 88/min, respirations are 22/min, and blood pressure is 138/82 mmHg. The patient appears pale. A systolic ejection murmur over the 2nd right intercostal space with radiation to the carotids is heard on auscultation. Laboratory tests are obtained and results are shown below.  
Laboratory value  Result 
 Hemoglobin  9.2 g/dL 
 Mean corpuscular volume (MCV)   88 fL 
 Platelet count  280,000/mm3  
 Reticulocyte count   4.2% 
Blood, plasma, serum 
Lactate dehydrogenase (LDH)  1380 U/L 
Which of the following are most likely seen on this patient’s peripheral blood smear?

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Autoimmune hemolytic anemia p. 110, 417

cephalosporins p. 186

Cold autoimmune hemolytic anemia p. 417


autoimmune hemolytic anemia and p. 417


Autoimmune hemolytic anemia refers to increased red blood cell hemolysis, or breakdown, that results when a person’s own antibodies target red blood cells for destruction.

And this results in a lower than normal amount of red blood cells anemia.

The disease is most often idiopathic, or without a known cause, but it can be related to a medication side effect, or an underlying disease process.

Normally, red blood cells, or RBCs, are made in the bone marrow and contain hemoglobin, which is an oxygen binding protein that delivers oxygen to tissues.

Red blood cells live about 100-120 days after which they are recycled in the bone marrow or consumed by macrophages in the spleen, liver, or lymphatic system.

Now, autoimmune hemolytic anemia is an extrinsic type of hemolytic anemia, because the immune system mistakenly believes our own red blood cells are foreign, or non-self, structures, so it secretes antibodies against proteins found on the RBC membrane.

If there had been a primary defect in the RBC membrane, then it would have been called an intrinsic hemolytic anemia.

And usually, hemolysis happens in the spleen or liver, so this is considered an extravascular hemolytic anemia - although in severe cases, RBC hemolysis can also happen intravascularly, or inside blood vessels.

Now, autoimmune hemolytic anemia gets classified as either warm or cold.

Warm is the more common type, and it’s when hemolysis occurs at temperatures greater than or equal to core human body temperature of 37º celsius.

Cold autoimmune hemolytic anemia is much rarer, and it occurs when people’s blood is exposed to cold temperatures, usually in the range of 0º to 10º celsius - like when a person goes out into cold weather during winter.

Warm autoimmune hemolytic anemia is almost always due to IgG antibodies, termed “warm agglutinins” that react with antigens, which are proteins on the surface of the red blood cell.


Autoimmune hemolytic anemia (AIHA) is a blood disorder that occurs when a person's own antibodies attack and destroy healthy red blood cells. The cause is not completely understood, but it may be associated with other conditions such as an infection, or leukemia. AIHA causes several symptoms, including fatigue, jaundice, shortness of breath, and an enlarged spleen.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  3. "Harrison's Principles of Internal Medicine" McGraw-Hill (2004)
  4. "Warm Autoimmune Hemolytic Anemia" Hematology/Oncology Clinics of North America (2015)
  5. "Cold Agglutinin-Mediated Autoimmune Hemolytic Anemia" Hematology/Oncology Clinics of North America (2015)
  6. "Autoimmune hemolytic anemia" American Journal of Hematology (2002)

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