Q. How do you tell apart aplastic anemia and pancytopenia?
A. This is an interesting question, because we’re comparing a distinct disease (aplastic anemia) with a generalized blood finding (pancytopenia).
Pancytopenia means that all of the cell lines (white cells, red cells, and platelets) are decreased in the blood. It’s an important blood finding, because it often indicates that something serious is going on in the marrow: either the marrow isn’t making enough cells, or it’s so full of other stuff (like the fibrosis you see in the image above) that it has no room to make normal cells). Sometimes, too, you can see pancytopenia with plain old splenomegaly (because the spleen is like a little home for the cells of the blood, and if enough of the cells stay at home in the spleen, you won’t see them out and about in the peripheral blood. So if you find pancytopenia in a patient, you need to work it up carefully to determine the cause (in other words, it’s not a diagnosis in and of itself – it indicates the presence of some underlying disease).
Aplastic anemia is a distinct, definable disease. In aplastic anemia, the bone marrow is “empty” (all that’s there are scattered lymphocytes and a rare hematopoietic precursor) and the blood shows a pancytopenia. Sometimes the cause can be determined (for example, the patient has taken a drug that can cause marrow aplasia), but often no particular cause can be found. In these cases, we use the fancy words “idiopathic” or “primary” instead of saying “we have no idea what’s causing this.”
So if you had a patient with pancytopenia, how would you figure out whether it was due to aplastic anemia or not? You’d have to do a bone marrow biopsy. You’d want to check the spleen first (to make sure the pancytopenia wasn’t due to a huge spleen); if the spleen was normal, then you’d need to do a bone marrow biopsy to see what was in the marrow (aplastic anemia, a bunch of fibrosis, etc.).