We talked recently about the direct antiglobulin test, which is a test used to find out whether a hemolytic anemia is immune-related or not. So let’s take a look at the immune hemolytic anemias!
The immune hemolytic anemias (also called autoimmune hemolytic anemias) come in two flavors: warm and cold, so named because the antibodies in each type react best at different temperatures. Which you would think is just a dumb laboratory observation, but as we’ll see, it actually has relevance to what’s going on in the patient.
Let’s start with warm autoimmune hemolytic anemia. The basic thing that’s happening in this anemia is that the patient, for some reason, is making IgG antibodies that stick to his/her red blood cells. These IgG antibodies work best at warm temperatures (37 degrees C, or 98.6 F – exactly at body temperature!). Most of the time there’s no known reason for the patient to be making the antibodies (instead of saying “we don’t know why,” though, say “idiopathic.” It sounds so much smarter.). Sometimes there is a known underlying cause – like lymphoma, leukemia, another autoimmune disease, an infection, or a drug (like penicillin) against which the patient is making antibodies (and those antibodies, unfortunately, also recognize epitopes on the patient’s red cells).
Whatever the cause, it’s not a good thing to have antibodies coating your red cells, because macrophages in the spleen see these antibody-coated red cells as yummy and gobble them up. Sometimes the macrophage eats the red cell whole, and sometimes it only gets a little nibble of it. In the latter instance, the red cell will lose a bit of membrane. When that happens, the red cell “rounds up” because it has less membrane to contain the same volume – and what you see is a spherocyte (as in the image above).
Warm autoimmune hemolytic anemia has no age, race, or sexual preference. It produces a variably severe anemia – sometimes mild, sometimes severe. The one thing that most patients have is a big spleen (because of all the eating going on in there).
And now, after reading the post on the DAT, you know how to diagnose an autoimmune hemolytic anemia! If the DAT is positive, you know it’s an autoimmune hemolytic anemia. The lab will be able to figure out whether it’s a warm or cold process; they’re smart that way.
Treatment involves eradicating the underlying cause, if possible (if it’s a drug, get rid of the drug). You can give the patient steroids, which inhibit immune reactions in general. If it’s really bad, and steroids aren’t helping, you can take out the spleen. Removing the spleen will remove the site of destruction, so the anemia should improve.
Next post: Cold autoimmune hemolytic anemia.
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