Pure Red Blood Cell Aplasia

Acquired pure red blood cell aplasia is a disorder of erythroid precursors that results in an isolated normocytic anemia. White blood cells and platelets are not affected. Symptoms result from anemia and include fatigue, lethargy, decreased exercise tolerance, and pallor. Diagnosis requires demonstration of peripheral normocytic anemia and a normocellular bone marrow biopsy with absence of erythroid precursors. Treatment usually involves treatment of underlying cause and in some cases thymectomy or immunosuppression.

Etiology

Pure red blood cell (RBC) aplasia is most often due to an inappropriate immune response causing suppression of erythropoiesis. Well-known causes include

• Thymomas
• Drugs (eg, tranquilizers, antiseizure drugs)
• Toxins (organic phosphates)
• Riboflavin deficiency
• Pregnancy
• HIV infection
• Lymphoproliferative diseases (chronic lymphocytic leukemia, large granular lymphocyte leukemia, chronic myeloid leukemia, Hodgkins lymphoma, non-Hodgkins lymphoma, multiple myeloma)
• ABO-mismatched bone marrow transplant
• Autoimmune disorders
• Collagen vascular diseases
• Solid tumors
• Parvovirus B19, particularly in immunocompromised patients such as those with HIV infection (the parvovirus binds to the blood group P antigen on erythroid precursors and is directly cytotoxic to the cells)
• Myelodysplastic syndrome (MDS)

Symptoms

Symptoms of pure RBC aplasia are generally mild and relate to the degree of the anemia or to the underlying disorder. The onset of pure red blood cell anemia usually is insidious, often occurring over weeks or months. Symptoms related to anemia include fatigue, lethargy, decreased exercise tolerance, and pallor.

Diagnosis

• Complete blood count (CBC), reticulocyte count
• Bone marrow examination

Pure RBC aplasia presents with a normocytic anemia but normal white blood cell and platelet counts. Reticulocytes are decreased.

The bone marrow reveals normal cellularity with a maturation arrest at the proerythroblast stage. In parvovirus B19 infection, giant pronormoblasts may be present. If possible, a marrow burst forming units-erythroid (BFU-E) assay should be obtained to differentiate benign causes of pure red blood cell aplasia from MDS .

Chest CT is indicated to evaluate for thymoma in the absence of another identified cause.

Treatment

• Immunosuppression
• Sometimes intravenous immunoglobulin (IVIG) or thymectomy

Pure RBC aplasia has been successfully managed with immunosuppressants (prednisone, cyclosporine, or cyclophosphamide), especially when an autoimmune mechanism is suspected

Pure RBC aplasia secondary to parvovirus infection is treated with intravenous immunoglobulin.

Thymectomy is performed in patients with thymoma-associated pure RBC aplasia; most patients improve but are not always cured.