Neutropenia and agranulocytosis
- Lesion
Too few neutrophils leave the body open to bacteria and fungi. The marrow tells whether they are not being made or are being destroyed.
What it is
Neutropenia is a fall in blood neutrophils; agranulocytosis is the extreme form, with almost none left. It arises either because the marrow makes too few granulocytes or because those released are destroyed, pooled in a large spleen or used up faster than they are replaced. Drugs are the commonest cause of agranulocytosis, and the danger is overwhelming infection that can kill within days.
Structure
- Marrow when precursors are destroyed or suppressed by a toxin: hypocellular, with few granulocytic precursors.
- Marrow when mature cells are destroyed in the periphery or maturation fails: hypercellular, full of young granulocytes.
- Infected tissue: ulcers and necrosis teeming with bacteria or fungi, with a thin or absent neutrophil response.
Step by step
- Production falls: marrow failure, chemotherapy, idiosyncratic drug toxicity, rare inherited defects of granulocyte maturation.
- Or maturation is ineffective: precursors die in the marrow, as in vitamin B12 or folate deficiency and myelodysplasia.
- Or released cells are lost: antibodies coat neutrophils, a big spleen traps them, or severe sepsis consumes them.
- The blood count drops; at very low counts the barrier to skin and gut bacteria is lost.
- Infection begins at mucosal surfaces (mouth, pharynx, gut, skin) and spreads to the blood.
Clinical notes
- Fever, chills, sore throat and mouth ulcers are the warning signs; with agranulocytosis sepsis can follow within hours.
- The risk of serious infection climbs steeply as the absolute neutrophil count falls toward the lowest range.
- Granulocyte colony-stimulating factor shortens the neutropenia that follows chemotherapy.
In the lab
- Absolute neutrophil count, not the percentage, defines the severity.
- Bone marrow biopsy separates a hypocellular marrow (production failure) from a hypercellular one (destruction or ineffective maturation).
Test yourself
Think of the answer, then tap the question to see it.
Why is the marrow hypercellular in megaloblastic anaemia despite neutropenia?
Granulocytic precursors are made in excess but die before maturing (ineffective granulopoiesis), so the marrow is full while the blood is empty.
What is the commonest cause of agranulocytosis?
Drug toxicity, either predictable (chemotherapy) or idiosyncratic.
What does an infected ulcer look like microscopically in agranulocytosis?
Necrotic tissue full of organisms with very few neutrophils, because the cells that make pus are missing.
Elsewhere in DurgiPedia
- Neutrophil
- White blood cells: types and functions
- The neutropenic and immunosuppressed patient (nursing)
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Agranulocytosis: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.