Concept
Agranulocytosis, also known as agranulosis or granulopenia, is an acute condition involving a severe and dangerous lowered white blood cell count (leukopenia, most commonly of neutrophils) and thus causing neutropenia in the circulating blood. It is a severe lack of one major class of infection-fighting white blood cells. People with this condition are at very high risk of serious infections due to their suppressed immune system. In agranulocytosis, the concentration of granulocytes (a major class of white blood cells that includes neutrophils, basophils, and eosinophils) drops below 200 cells/mm3 of blood. Agranulocytosis may be asymptomatic, or may clinically present with sudden fever, rigors and sore throat. Infection of any organ may be rapidly progressive (e.g., pneumonia, urinary tract infection). Sepsis may also progress rapidly. A large number of drugs have been associated with agranulocytosis, including antiepileptics (such as carbamazepine and valproate), antithyroid drugs (carbimazole, thiamazole, and propylthiouracil), antibiotics (penicillin, chloramphenicol and trimethoprim/sulfamethoxazole), H2 blockers (cimetidine, famotidine, nizatidine, ranitidine), ACE inhibitors (benazepril), cytotoxic drugs, gold salts, analgesics (aminophenazone, indomethacin, naproxen, phenylbutazone, metamizole), mebendazole, allopurinol, the antidepressants mianserin and mirtazapine, and some antipsychotics. The atypical antipsychotic clozapine in particular is largely restricted to treatment-resistant cases and mandatory blood count monitoring in most countries. Although the reaction is generally idiosyncratic rather than proportional, experts recommend that patients using these drugs be told about the symptoms of agranulocytosis-related infection, such as a sore throat and a fever. The Centers for Disease Control and Prevention traced outbreaks of agranulocytosis among cocaine users, in the US and Canada between March 2008 and November 2009, to the presence of levamisole in the drug supply.