Pathology
Aplastic Anaemia
Aplastic anaemia for MBBS and NEET-PG: causes of marrow failure, pancytopenia with low reticulocytes, the hypocellular marrow, and differentiation from other causes of pancytopenia, mapped to NMC codes PA17.1 and PA17.2.
MedNext Academy | 3 min read
Aplastic Anaemia
Aplastic anaemia for MBBS and NEET-PG: causes of marrow failure, pancytopenia with low reticulocytes, the hypocellular marrow, and differentiation from other causes of pancytopenia, mapped to NMC codes PA17.1 and PA17.2.
This chapter covers aplastic anaemia and marrow failure. It describes the causes, the peripheral blood picture of pancytopenia with a low reticulocyte count, the diagnostic hypocellular marrow on trephine biopsy, and the differentiation of aplastic anaemia from other causes of pancytopenia.
High-yield: Aplastic Anaemia
- Aplastic anaemia is bone marrow failure producing pancytopenia, a reduction in red cells, white cells and platelets together.
- The marrow in aplastic anaemia is hypocellular and largely replaced by fat, with no infiltration or fibrosis.
- The peripheral blood shows pancytopenia with a low reticulocyte count, reflecting failed production rather than destruction.
- About half of cases are idiopathic, thought to be immune-mediated destruction of stem cells.
- Recognised causes include drugs such as chloramphenicol, cytotoxics, benzene, ionising radiation and viral hepatitis.
- Fanconi anaemia is an inherited form of aplastic anaemia associated with congenital anomalies and a raised cancer risk.
- Patients present with anaemia (fatigue and pallor), infections (from neutropenia) and bleeding (from thrombocytopenia).
- A bone marrow trephine biopsy is essential to confirm the hypocellular marrow, since aspirate may give a dry tap.
- Aplastic anaemia must be distinguished from other causes of pancytopenia such as leukaemia, myelodysplasia and marrow infiltration.
- Unlike leukaemia, aplastic anaemia shows no blast cells and no organomegaly.
- Severity is graded by the degree of neutropenia, thrombocytopenia and reticulocytopenia.
- Allogeneic stem cell transplantation and immunosuppressive therapy are the definitive treatments for severe disease.
- Pure red cell aplasia affects only the erythroid line and is associated with thymoma and parvovirus B19 infection.
- Paroxysmal nocturnal haemoglobinuria and myelodysplasia can evolve from or coexist with aplastic anaemia.
Aplastic anaemia at a glance
- **Blood:** Pancytopenia with a low reticulocyte count.
- **Marrow:** Hypocellular, fatty; no blasts, fibrosis or infiltration.
- **Causes:** Idiopathic, drugs (chloramphenicol), benzene, radiation, viral hepatitis; inherited Fanconi anaemia.
- **Distinguish from:** Leukaemia, myelodysplasia and marrow infiltration, which show blasts or abnormal cells.
NMC competencies in this chapter
- **PA17.1:** Bone marrow findings in aplastic anaemia
- **PA17.2:** Peripheral blood picture in aplastic anaemia and pancytopenia
Frequently Asked Questions
What is aplastic anaemia?
Bone marrow failure that produces pancytopenia, a fall in all three blood cell lines, with a hypocellular fatty marrow.
How is the marrow described in aplastic anaemia?
Hypocellular and replaced by fat, without blast cells, fibrosis or infiltration, best shown on a trephine biopsy.
What are common causes of aplastic anaemia?
Many cases are idiopathic and immune-mediated, and known causes include chloramphenicol and cytotoxic drugs, benzene, radiation and viral hepatitis.
How is aplastic anaemia distinguished from leukaemia?
Aplastic anaemia shows a hypocellular marrow with no blast cells and no organomegaly, while leukaemia shows blasts and often hepatosplenomegaly.
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