Pure Red Cell Aplasia
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Direct answer
Pure red cell aplasia is isolated erythroid failure, producing an anaemia (usually normocytic normochromic) with reticulocytopenia while white cell and platelet counts stay normal. The bone marrow shows absent or markedly reduced erythroid precursors. Its main causes are thymoma, large granular lymphocytic leukaemia, parvovirus B19 infection, drugs and, in children, congenital Diamond-Blackfan anaemia.
What you must remember
- Defining picture: anaemia with a very low reticulocyte count, normal leucocytes and platelets, and absent erythroid precursors in the marrow.
- Diamond-Blackfan anaemia: congenital, presenting in infancy with ribosomal protein gene mutations such as RPS19, often with physical anomalies, macrocytosis and raised fetal haemoglobin.
- Thymoma: a classic acquired association in adults, linked to T-cell mediated suppression of erythropoiesis, and thymectomy helps only some patients.
- Large granular lymphocytic leukaemia: a clonal T-cell or NK-cell disorder that suppresses erythroid precursors, which needs flow cytometry to diagnose.
- Parvovirus B19: infects erythroid progenitors, causing transient aplastic crisis in haemolytic anaemia and chronic PRCA in immunocompromised patients.
- Drugs: azathioprine, phenytoin and ribavirin are well-recognised causes of pure red cell aplasia.
- Anti-erythropoietin antibodies: erythropoiesis-stimulating agents can induce neutralising antibodies that cause pure red cell aplasia, particularly with subcutaneous formulations.
- Treatment: remove the cause, give IVIG for parvovirus, and use immunosuppression with ciclosporin or steroids, with transfusion as needed.
A diagnostic workflow for isolated erythroid failure
Pure red cell aplasia is a diagnosis of exclusion, and each step narrows the cause without delaying supportive care. The approach below moves from the blood count to the marrow and then to specific causes.
- Confirm the pattern: check for reticulocytopenia with normal leucocytes and platelets, since low white cells or platelets point to a different diagnosis.
- Examine the marrow: erythroid precursors are absent or markedly reduced, while granulocytic and megakaryocytic lines are preserved.
- Check the age and features: congenital disease presents in infancy with macrocytosis, raised fetal haemoglobin and physical anomalies, suggesting Diamond-Blackfan anaemia.
- Image the mediastinum: CT of the chest in adults identifies a thymoma, which is a common and treatable cause.
- Test for parvovirus: PCR on blood or marrow detects persistent infection, especially in immunosuppressed patients.
- Review drugs and ESA exposure: stop azathioprine, phenytoin or ribavirin where possible, and test for anti-erythropoietin antibodies in treated patients.
- Exclude clonal disease: flow cytometry for large granular lymphocytes and chronic lymphocytic leukaemia identifies a lymphoid cause.
Where the exam tries to catch you
Pure red cell aplasia questions turn on the normal white count and on the associated tumour or infection.
- Trap: labelling the picture as pancytopenia because the patient is anaemic Correct: leucocyte and platelet counts are normal in pure red cell aplasia, so a low white count points elsewhere.
- Trap: treating chronic parvovirus-related aplasia with steroids alone Correct: immunosuppressed patients with persistent parvovirus infection respond to IVIG, which clears the virus.
- Trap: ignoring a mediastinal mass in an adult with isolated anaemia Correct: thymoma must be sought, because thymectomy can reverse the aplasia in some patients.
- Trap: attributing a child's aplasia to an acquired cause without looking for congenital features Correct: Diamond-Blackfan anaemia presents in infancy with physical anomalies, macrocytosis and raised fetal haemoglobin.
Frequently asked questions
Which tumour is classically associated with pure red cell aplasia?
Thymoma is the classic tumour associated with pure red cell aplasia, linked to T-cell mediated suppression of erythropoiesis. Thymectomy and immunosuppression are the main approaches, and the anaemia improves after surgery in only a proportion of patients.
How does parvovirus B19 cause pure red cell aplasia?
Parvovirus B19 infects erythroid progenitor cells that carry the P antigen, destroying them and halting red cell production. It causes transient aplastic crisis in haemolytic anaemia and persistent pure red cell aplasia in immunocompromised patients, which is treated with intravenous immunoglobulin.
What is Diamond-Blackfan anaemia?
Diamond-Blackfan anaemia is a congenital pure red cell aplasia presenting in infancy, usually from ribosomal protein gene mutations such as RPS19. Patients often have physical anomalies, macrocytosis and raised fetal haemoglobin, and corticosteroids are the first-line treatment.
Which drugs can cause pure red cell aplasia?
Azathioprine, phenytoin and ribavirin are well-recognised drug causes of pure red cell aplasia. Erythropoiesis-stimulating agents can also cause it through neutralising anti-erythropoietin antibodies, particularly with subcutaneous formulations.
What is the peripheral blood picture in pure red cell aplasia?
Pure red cell aplasia shows a normocytic normochromic anaemia with a very low reticulocyte count, while white cell and platelet counts remain normal. The bone marrow shows absent or markedly reduced erythroid precursors, which distinguishes it from other anaemias.