Concentrations of granulocytes (a class that includes neutrophils, basophils and eosinophils) can often drop to below 500 cells/mm³ of blood), less than a sixth of the reference value of 3-10 x 103 cells/mm³.
A large number of drugs have been associated with agranulocytosis, including antiepileptics, antithyroid drugs (carbimazole and methimazole), metamizole, antibiotics (penicillin, chloramphenicol and co-trimoxazole), cytotoxic drugs, gold, NSAIDs (indomethacin, naproxen, phenylbutazone), the antidepressant mirtazapine, and some antipsychotics (the atypical antipsychotic clozapine). Clozapine users in the US must be nationally registered for monitoring of low WBC and absolute neutrophil counts (ANC). Although the reaction is generally idiosyncratic rather than proportional, experts recommend that patients be told about the symptoms of agranulocytosis-related infection, such as a sore throat and a fever.
Neutropenia and agranulocytosis are associated with gum disease.
The neutrophil count is below 500 and can reach 0 cells/mm3. Other series are normally spared. The myelogram (bone marrow sample) shows normocellular blood marrow with promyelocyte's maturation arrest. To formally diagnose agranulocytosis, other pathologies with a similar presentation must be excluded, such as aplastic anemia, paroxysmal nocturnal hemoglobinuria, myelodysplasia and leukemias. This requires a bone marrow examination.
Infection in patients with low white blood cell counts is usually treated urgently, and usually includes a broad-spectrum penicillin or cephalosporin (piperacillin-tazobactam, ceftazidime or ticarcillin clavulanate) or meropenem in combination with gentamycin or amikacin.
If the patient remains febrile after 4-5 days and no causative organism for the infection has been identified, antibiotics are generally changed to a glycopeptide (e.g. vancomycin), and subsequently an antifungal agent (e.g. amphotericin B) is added to the regimen. In agranulocytosis, the use of recombinant G-CSF (filgrastim) often results in hematologic recovery.
Transfusion of granulocytes would have been a solution to the problem. However, granulocytes live only ~10 hours in the circulation (for days in spleen or other tissue), which gives a very short-lasting effect. In addition, there are many complications of such a procedure.