agranulocytosis

Agranulocytosis is a serious hematologic condition characterized by an extremely low number of neutrophils, increasing the risk of severe infections. The defining laboratory feature is an absolute neutrophil count below 500 cells per microliter (0.5 × 10^9/L). Patients may be asymptomatic until an infection develops, at which point fever, sore throat, mucosal ulcers, and signs of sepsis can occur.

Most cases are drug-induced, though agranulocytosis can also result from autoimmune disorders, bone marrow disorders, infections, or nutritional deficiencies. Medications commonly implicated include certain antipsychotics (notably clozapine), antithyroid drugs (methimazole, propylthiouracil), anticonvulsants (carbamazepine), sulfonamides, and cytotoxic chemotherapy. Onset is often days to weeks after exposure, but can occur later with chronic treatment or after dose changes. Recovery typically begins after discontinuation of the offending agent and supportive care.

Diagnosis rests on a complete blood count with differential showing marked neutropenia (ANC < 500/µL). In selected cases, bone marrow examination may reveal reduced granulopoiesis or maturation arrest. Evaluation for concurrent infection is essential, and patients with fever or systemic symptoms require prompt empiric broad-spectrum antibiotics, with infection control measures as indicated.

Management includes immediate withdrawal of the suspected drug, supportive care, infection prevention, and frequently the use of growth factors such as granulocyte colony-stimulating factor to hasten neutrophil recovery in selected patients. Prognosis depends on the degree of neutropenia, timeliness of identification, and prompt treatment of infections; overall outcomes have improved with early intervention and standardized monitoring, particularly for high-risk medications. Prevention relies on regular monitoring for known drug-associated risks and patient education.