Synopsis
Grade neutrophil deficiency, recognise infection despite muted signs, identify drug, immune, nutritional, infective and marrow causes, and stop culpable exposure while supporting safe recovery.
- Neutropenia is a reduced absolute neutrophil count, commonly graded as mild 1.0–1.5, moderate 0.5–1.0 and severe below 0.5 × 10^9/L, with context and duration determining risk.
- Agranulocytosis usually denotes profound neutropenia, often drug induced, with a high risk of rapidly progressive bacterial or fungal infection.
- Repeat an unexpected result and inspect the film, but treat fever or physiological instability immediately rather than waiting to prove persistence.
- Medicine reconciliation must include recent courses and stopped drugs: antithyroid medicines, clozapine, metamizole exposure abroad, sulfasalazine, antiepileptics, antimicrobials and cytotoxic or immune therapies.
- Viral infection can transiently lower neutrophils, while HIV, hepatitis, EBV or CMV may produce a prolonged pattern guided by exposure and symptoms.
- B12, folate and copper deficiency can suppress several lines; isolated neutropenia with normal indices makes a global nutritional cause less likely but not impossible.
- Duffy-null-associated neutrophil counts are a healthy inherited reference variant common in some ancestries and should not be labelled disease after appropriate assessment.
- Lymphadenopathy, splenomegaly, blasts, dysplasia, other cytopenias or progressive constitutional symptoms raise marrow malignancy, autoimmune disease or hypersplenism.
- Bone-marrow examination is used for unexplained persistent, severe or multilineage cytopenia, not automatically for every stable mild count.
- Granulocyte colony-stimulating factor is used for defined chemotherapy, congenital or severe drug-related settings under specialist guidance and does not replace antibiotics in sepsis.
Key red flags
Hypotension, confusion, raised lactate or hypoxia with neutropenia needs immediate antibiotics and organ support regardless of temperature.
Investigation priorities
Confirm severity and detect other lineage or morphological clues.
Management branches
A low neutrophil count is newly reported or found during illness.
- Assess temperature, haemodynamics, mucosa, skin, lines, respiratory and perianal symptoms immediately and treat septic physiology through the acute pathway.
- Repeat count and film, retrieve prior values and grade depth and duration while taking cultures and giving antibiotics when fever or instability is present.
- Apply medicine-specific emergency rules, withholding a plausible culprit and coordinating essential-disease replacement with the responsible specialist.
Key medicines
FilgrastimHaematology or oncology uses a weight-based subcutaneous regimen for a defined chemotherapy, congenital or severe drug-related indication, adjusting duration to neutrophil recovery and clinical context.Bone pain, splenic enlargement or rupture, leucocytosis, lung injury and sickle crisis are recognised; it does not replace antibiotics or source control in infection.
Culprit medicine withdrawalWithhold further doses immediately under the product-specific agranulocytosis pathway and do not rechallenge unless a national monitoring service and senior specialist explicitly authorise it.Coordinate clozapine, antithyroid or seizure treatment alternatives urgently; document the reaction and avoid inadvertent exposure to the same or cross-reactive agent.