granulocytopenia

Granulocytopenia refers to a decrease in circulating granulocytes, a category of white blood cells that includes neutrophils, eosinophils, and basophils. In clinical practice, the term is often used interchangeably with neutropenia since neutrophils comprise the majority of granulocytes and are the primary defense against bacterial and fungal pathogens. Causes include: bone marrow suppression (chemotherapy, radiation, aplastic anemia, leukemia infiltration), drug-induced (e.g., clozapine, methimazole/PTU, sulfonamides, carbamazepine), infections (viral suppression of marrow - HIV, EBV, parvovirus B19), autoimmune destruction (e.g., in lupus, Felty syndrome), nutritional deficiencies (B12, folate), and congenital disorders (e.g., cyclic neutropenia, Kostmann syndrome). Severity is classified by absolute neutrophil count (ANC): mild (1000-1500), moderate (500-1000), severe (<500/µL) - termed agranulocytosis when severe and often drug-induced. Clinical significance: patients are at increased risk for bacterial infections (especially skin, respiratory, GI tract) and opportunistic fungal infections (Candida, Aspergillus). Febrile neutropenia (fever + ANC <500) requires immediate broad-spectrum antibiotics due to risk of rapid sepsis, as the typical inflammatory response is blunted, masking classic signs of infection. Management includes treating underlying cause, G-CSF (filgrastim) to stimulate granulocyte production in chemotherapy-induced cases, and prophylactic antimicrobials in high-risk patients. Key boards associations: clozapine requires mandatory ANC monitoring due to agranulocytosis risk; methimazole/PTU can cause agranulocytosis; chemotherapy nadir typically occurs 7-14 days post-treatment.