Much of the time, when a patient has a neutrophilia, it is due to infection. But are there any clues on the blood smear that would make that diagnosis more definitive?

Well, yes, as a matter of fact, there are. These clues are called toxic changes and they encompass three main findings: toxic granulation (as seen above), Dohle bodies (also present above – look closely), and cytoplasmic vacuolization. If you see any of these changes, you can be quite certain that the patient has an infection.

Toxic granulation is the accumulation of big, dark granules in segmented neutrophils (or, sometimes, in earlier neutrophil precursors). It is likely due to the demand placed on the marrow to get those neutrophils out in the circulation as soon as possible in order to fight the infection. Under those conditions, the myeloblasts and promyelocytes (the dividing cells of the neutrophil lineage) say, “Okay, fine. You want segmented neutrophils out in the circulation immediately? I’ll quit spending my time dividing so much, and I’ll just mature!” This is a good strategy for getting mature neutrophils out of the marrow as quickly as possible. In the process of this kind of rushing around, the big fat dark primary granules present in the promyelocytes do not get diluted out like they normally would (when the promyelocytes are taking their time, and dividing over and over again before maturing, the dark granules get spread out among many generations of cells). Instead, they are retained in the cell, and you can see them even in the mature, segmented neutrophil descendents of these harried promyelocytes.

Cool, huh?

The two other changes are Dohle bodies (pretty sky-blue cytoplasmic inclusions in neutrophils; look closely at the above image – you can just barely make one out) and cytoplasmic vacuolization (an ominous change, by the way – if you see a lot of cytoplasmic vacuolization, and particularly if it is increasing over time, watch out.).  These changes, too, are quite specific for infection.