# Neutropenia and Agranulocytosis

> Neutropenia and agranulocytosis for NEET-PG Medicine covers drug, ethnic and cyclic causes, neutrophil count thresholds and febrile neutropenia care.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/neutropenia-and-agranulocytosis
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Hoffbrand's Essential Haematology; Harrison's Principles of Internal Medicine; Goldfrank's Toxicologic Emergencies
- How to cite: "Neutropenia and Agranulocytosis", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/neutropenia-and-agranulocytosis

## Direct answer

Neutropenia is an absolute neutrophil count below 1500 per microlitre, and agranulocytosis is a severe fall, usually below 500 per microlitre. Drugs are the commonest acquired cause, with clozapine and carbimazole as classic examples, while benign ethnic neutropenia and cyclic neutropenia explain many isolated low counts. Management starts with stopping any offending drug and treating fever as an emergency, because infection is the main threat.

## What you must remember

- **Threshold:** an absolute neutrophil count (ANC) below 1500 per microlitre defines neutropenia, and below 500 per microlitre carries the greatest risk of serious infection.
- **Drug-induced causes:** clozapine, carbimazole, methimazole, propylthiouracil, sulfasalazine, chloramphenicol and dapsone are classic offenders, and stopping the drug is the first step.
- **Benign ethnic neutropenia:** a stable low count, common in people of African and Middle Eastern ancestry, linked to the Duffy-null genotype and not associated with raised infection risk.
- **Cyclic neutropenia:** neutrophil counts fall at a roughly 21-day interval, usually from ELANE mutations, and the pattern is seen only on serial counts.
- **Febrile neutropenia:** fever with an ANC below 500 per microlitre, or expected to fall below it, needs urgent empirical broad-spectrum antibiotics after blood cultures.
- **Severe congenital neutropenia:** maturation arrest at the promyelocyte stage, including Kostmann syndrome, which responds to G-CSF in most patients.
- **Growth factor use:** filgrastim is reserved for severe neutropenia with infection, chemotherapy-induced neutropenia and selected congenital forms, not for every low count.

## Approach to a low neutrophil count

A 34-year-old woman on clozapine for schizophrenia has a routine count showing an ANC of 900 per microlitre and no fever. The first task is to decide whether the low count is real, drug-related, constitutional or marrow-based.

1. **Confirm the count:** repeat the full blood count with a peripheral smear to check that the neutropenia is real and to look for blasts or dysplasia.
2. **Review every drug:** list new and recently stopped medicines, because idiosyncratic drug-induced neutropenia often appears within weeks to months of starting the drug.
3. **Check the pattern:** a stable low count in a well patient of African or Middle Eastern ancestry suggests benign ethnic neutropenia, while a regular fall about every three weeks suggests cyclic neutropenia.
4. **Assess infection risk:** fever, mouth ulcers, perianal pain or sepsis signs make this an emergency that needs immediate antibiotics without waiting for culture results.
5. **Look for marrow causes:** blasts, pancytopenia or hepatosplenomegaly prompt marrow examination for leukaemia, aplastic anaemia or infiltration.
6. **Plan monitoring:** for clozapine, follow the drug's specific neutrophil monitoring protocol, and stop the drug at the defined threshold rather than reacting only to fever.

## Where the exam tries to catch you

Neutropenia questions usually turn on whether the low count is harmless or dangerous.

- **Trap:** treating benign ethnic neutropenia with G-CSF or steroids — **Correct:** a stable count in a well patient needs reassurance and documentation, not growth factors.
- **Trap:** waiting for the ANC or culture result before giving antibiotics in febrile neutropenia — **Correct:** empirical broad-spectrum antibiotics start promptly, since sepsis can progress within hours.
- **Trap:** labelling a regular 21-day fall in counts as drug-induced — **Correct:** a predictable cycle points to cyclic neutropenia, and serial counts confirm it.
- **Trap:** continuing carbimazole or clozapine after agranulocytosis is found — **Correct:** the offending drug is stopped first, and the agent is avoided in future.

## Frequently asked questions

### Which drugs most commonly cause drug-induced agranulocytosis?

Clozapine, carbimazole, methimazole, propylthiouracil, sulfasalazine and dapsone are among the classic causes of drug-induced agranulocytosis. Clozapine is the best-known example that requires regular neutrophil monitoring. Stopping the offending drug is the first and most important step in management.

### What is the difference between neutropenia and agranulocytosis?

Neutropenia means an absolute neutrophil count below 1500 per microlitre, while agranulocytosis is a much more severe fall, usually below 500 per microlitre. Agranulocytosis carries a considerably higher risk of life-threatening infection than mild neutropenia. Both are assessed on the absolute count, not the total white cell count.

### Is benign ethnic neutropenia dangerous?

Benign ethnic neutropenia is not usually dangerous, because the neutrophil count is low but infection risk is not raised. It is common in people of African and Middle Eastern ancestry and is linked to the Duffy-null genotype. Recognising it avoids unnecessary investigation and treatment with growth factors or steroids.

### How is febrile neutropenia defined and managed?

Febrile neutropenia is a temperature of 38.3 °C once, or 38 °C sustained over an hour, with an ANC below 500 per microlitre or expected to fall below it. Blood cultures are taken and empirical broad-spectrum antibiotics are started without waiting for culture results. Early treatment is the key to preventing deaths from sepsis.

### What is cyclic neutropenia and how is it recognised?

Cyclic neutropenia is a rare disorder in which neutrophil counts fall regularly about every 21 days, usually because of ELANE mutations. It is recognised by serial counts over several weeks that show the predictable cycle. Counts recover between episodes, and treatment is supportive, with G-CSF reserved for patients with serious infections.