What is aplastic anemia?

Aplastic anemia happens when your bone marrow stops making enough blood-forming stem cells. Most experts believe aplastic anemia happens when your immune system attacks and kills your stem cells. This causes you to have low blood counts for all three types of blood cells. Low blood counts result in symptoms such as fatigue, tiredness, risk for infections, bleeding and bruising. This disease can be classified as moderate (MAA), severe (SAA) or very severe (VAA) depending on how low your blood counts are.