[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Red cells and bleeding disorders](https://durgical.com/en/general-pathology/areas/red-cells/) › Aplastic anaemia

# Aplastic anaemia

- Lesion

The marrow empties of blood-forming cells and fills with fat. All counts fall; most cases are an immune attack on the stem cells.

Updated Nov 12, 2026

## Key points

- Pancytopenia, hypocellular marrow mainly of fat, no dysplasia, no splenomegaly.
- Immune mechanism: T cells produce interferon-γ and TNF that destroy stem cells; antithymocyte globulin and cyclosporine work.
- Causes: benzene, chemotherapy, chloramphenicol and other idiosyncratic drugs, non-A–E hepatitis, radiation.
- Fanconi anaemia: DNA repair defect with thumb and radius anomalies, short stature and marrow failure in childhood.
- Telomerase mutations or short telomeres in a fraction of adult cases; PNH clones are common.

## What it is

Aplastic anaemia is marrow failure with pancytopenia and a hypocellular, fatty marrow, caused by loss of haematopoietic stem cells rather than replacement by tumour. Most acquired cases are idiopathic and immune-mediated: activated T cells release interferon-γ and TNF that kill stem cells, and immunosuppression restores counts in many patients. Other causes are drugs and chemicals (dose-related or idiosyncratic), viral infections (especially seronegative hepatitis), radiation and inherited syndromes such as Fanconi anaemia and telomerase defects.

## Structure

- Marrow biopsy: less than about a quarter of normal cellularity, mainly fat with scattered lymphocytes and plasma cells.
- Aspirate: often dry or diluted; residual cells are not dysplastic.
- Blood: normocytic or slightly macrocytic anaemia, neutropenia, thrombocytopenia, low reticulocytes.

## Step by step

- A drug, virus or unknown trigger alters stem cells or presents new antigens.
- Autoreactive T cells (Th1 and cytotoxic) are activated.
- Interferon-γ and TNF trigger apoptosis of stem and progenitor cells.
- Alternatively, inherited DNA repair or telomere defects exhaust the stem cell pool.
- Fat replaces the marrow; all lineages fall: anaemia, infections, bleeding.

## Causes of aplastic anaemia

| Group | Examples | Key point |
| --- | --- | --- |
| [Inherited: Fanconi anaemia](https://durgical.com/en/conditions/fanconi-anaemia/) | FANC gene defects in DNA crosslink repair | Congenital anomalies, cancer risk |
| [Inherited: telomere biology disorders](https://durgical.com/en/conditions/dyskeratosis-congenita-and-other-telomere-biology-disorders/) | Dyskeratosis congenita, TERT and TERC mutations | Nail dystrophy, oral leukoplakia, lung fibrosis |
| Acquired immune (idiopathic) | Most adult cases | Responds to immunosuppression |
| Drugs, chemicals, radiation, viruses | Chemotherapy, benzene, chloramphenicol, radiation, seronegative hepatitis | Some dose-related and reversible, some idiosyncratic |

## Clinical notes

- Pallor, petechiae, bleeding gums and repeated infections in a patient without splenomegaly.
- Stem cell transplantation is the treatment of choice when a donor exists; immunosuppression otherwise.

## Memory aid

Empty marrow, fat everywhere, a quiet spleen: suspect T cells eating the stem cells.

## Test yourself

Think of the answer, then tap the question to see it.

## What finding on biopsy separates aplastic anaemia from hypocellular MDS or leukaemia?

A fat-filled hypocellular marrow without dysplasia or excess blasts.

## What evidence supports an immune cause of most acquired aplastic anaemia?

Many patients recover counts after antithymocyte globulin and cyclosporine, and T cells produce interferon-γ that kills stem cells.

## Which physical finding argues against aplastic anaemia?

Splenomegaly.

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## Elsewhere in DurgiPedia

- [Hematopoiesis and bone marrow](https://durgical.com/en/histology/hematopoiesis-and-bone-marrow/)
- [CD8⁺ cytotoxic T cell](https://durgical.com/en/immunology/cd8-cytotoxic-t-cell/)

## Connections

## Related 5

- [Paroxysmal nocturnal haemoglobinuria](https://durgical.com/en/general-pathology/paroxysmal-nocturnal-haemoglobinuria/)
- [Myelodysplastic neoplasms](https://durgical.com/en/general-pathology/myelodysplastic-neoplasms/)
- [Cellular aging: telomeres, DNA damage, senescence and proteostasis](https://durgical.com/en/general-pathology/cellular-aging-telomeres-dna-damage-senescence-and-proteostasis/)
- [Ionizing radiation injury](https://durgical.com/en/general-pathology/ionizing-radiation-injury/)
- [Neutropenia and agranulocytosis](https://durgical.com/en/general-pathology/neutropenia-and-agranulocytosis/)

## Related conditions 6

- [Aplastic anaemia](https://durgical.com/en/conditions/aplastic-anaemia/)
- [Fanconi anaemia](https://durgical.com/en/conditions/fanconi-anaemia/)
- [Dyskeratosis congenita and other telomere biology disorders](https://durgical.com/en/conditions/dyskeratosis-congenita-and-other-telomere-biology-disorders/)
- [Paroxysmal nocturnal haemoglobinuria](https://durgical.com/en/conditions/paroxysmal-nocturnal-haemoglobinuria/)
- [Viral hepatitis](https://durgical.com/en/conditions/viral-hepatitis/)
- [Febrile neutropenia](https://durgical.com/en/conditions/febrile-neutropenia/)

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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: [Aplastic Anemia | MedlinePlus](https://medlineplus.gov/aplasticanemia.html) (MedlinePlus, US National Library of Medicine, 2026); [Fanconi anemia: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/fanconi-anemia/) (MedlinePlus, US National Library of Medicine, 2026).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/aplastic-anaemia/