Q. I am wondering if you could differentiate between what extracorpuscular and intracorpuscular anemia are in terms of where they occur and why there is a difference in the two types.

A. Sure! Intracorpuscular just means within the red cell itself – so an intracorpuscular anemia is one that is due to some defect in the red cell. Extracorpuscular means outside the red cell – so an extracorpuscular anemia is one in which the red cell itself is normal, but it’s being attacked by something outside of it. Both of these anemias are hemolytic anemias – they just differ in what is causing the hemolysis (something within the red cell, or something outside the red cell). 

So the intracorpuscular anemias all have some kind of red cell defect (these are all inherited diseases by the way). The defect can be in the red cell cytoskeleton (like hereditary spherocytosis and hereditary elliptocytosis) – something is wrong with it, making the red cell membrane unstable. Or it can be an enzyme deficiency (like glucose 6 phosphate dehydrogenase deficiency, where the patient is missing an enzyme that detoxifies the red cell). Or it can be some kind of defect in globin structure or synthesis (like sickle cell anemia, in which beta globin chains are messed up, or thalassemia, in which the patient can’t make enough alpha or beta globin chains).

Extracorpuscular anemias are those in which something outside of the red cell is causing hemolysis (these are all acquired, not inherited!). The thing causing hemolysis can be an antibody (like you see in in warm and cold autoimmune hemolytic anemia), a bug of some kind (like you see in malaria), a drug (tons of drugs can cause hemolysis), or fibrin strands in the blood vessels (this happens in microangiopathic hemolytic anemia).

I hope that makes sense! I included links in case you want more info on some of the anemias. Let me know if it still doesn’t make sense!