Pure red cell aplasia is a rare hematologic disorder characterized by a severe and selective reduction or absence of erythroid production in the bone marrow, with preservation of the granulocytic and megakaryocytic lineages. Clinically, it presents as a normocytic or macrocytic anemia with low reticulocyte count, in the absence of significant leukopenia or thrombocytopenia.
Although it shares some features with aplastic anemia, pure red cell aplasia is clearly distinct due to the isolated involvement of the red blood cell lineage. Clinical management varies depending on the etiology, which may include autoimmune, infectious, pharmacological, or neoplastic causes.
The causes of pure red cell aplasia can be divided into primary (idiopathic or autoimmune) and secondary to pathological conditions or environmental exposures.
The pathogenesis typically involves immune-mediated destruction of erythroid precursors or direct viral inhibition of their replication, with mechanisms varying depending on the causative agent.
The predominant pathophysiological mechanism in acquired pure red cell aplasia is autoimmune, involving the production of antibodies or cytotoxic T lymphocytes directed against erythroid progenitors.
In cases associated with viral infections such as Parvovirus B19, the virus selectively infects erythroid progenitors (particularly BFU-E and CFU-E stages), blocking their proliferation and inducing apoptosis.
Histopathologically, the bone marrow shows a drastic reduction or absence of erythroid precursors, with preserved granulopoiesis and megakaryopoiesis. This finding is essential for distinguishing pure red cell aplasia from other causes of severe anemia.
Pure red cell aplasia manifests with symptoms typical of severe anemia, while manifestations related to neutropenia or thrombocytopenia are absent.
Key points to investigate:
Symptoms arise from severe anemia and include:
Fever or infectious signs should raise suspicion of an underlying viral infection, while the presence of mediastinal masses suggests associated thymoma.
The diagnosis of pure red cell aplasia is based on identifying a severe anemia associated with a marked reticulocytopenia, in a context where white blood cells and platelets are normal or only slightly reduced. Clinical suspicion should arise when encountering disproportionate anemia compared to preserved other blood cell lines, especially in immunosuppressed patients, thymoma carriers, or those with known autoimmune diseases.
The diagnostic process progresses from first-level tests to specialized investigations.
The complete blood count shows a normocytic or slightly macrocytic anemia with a dramatically reduced reticulocyte count (<1%), while white blood cells and platelets are within normal limits or only slightly decreased. The peripheral smear confirms the absence of significant morphological abnormalities, excluding dysplastic syndromes.
Definitive diagnosis is obtained through bone marrow examination: the aspirate and biopsy document a near-total absence of erythroid precursors with preserved granulopoiesis and megakaryopoiesis. Unlike aplastic anemia, the overall marrow cellularity is normal or only mildly reduced, without evidence of neoplastic infiltration or significant fibrosis.
In cases of suspected infection, especially in immunocompromised patients, testing for Parvovirus B19 is crucial. This can be performed via PCR for viral DNA on peripheral blood or bone marrow, or by measuring specific IgM antibodies in serum.
These examinations are indicated to rule out other causes of selective erythroid insufficiency, such as hypocellular myelodysplastic syndromes or early-stage acute leukemias.
In patients with clinical or laboratory suspicion of thymoma, chest CT scan is indicated to search for mediastinal masses, given the known association between pure red cell aplasia and thymic tumors.
Pure red cell aplasia must be distinguished from other causes of severe anemia with reticulocytopenia:
The key diagnostic finding is the selective suppression of erythropoiesis with preservation of other blood cell lines.
Treatment of pure red cell aplasia is closely linked to the underlying etiology and requires a targeted approach for each clinical situation.
In idiopathic autoimmune forms, which account for a significant proportion of cases, first-line therapy consists of high-dose corticosteroids (usually prednisone), aiming to suppress the abnormal immune response responsible for the destruction of erythroid precursors. In refractory or relapsing cases, immunosuppressants such as cyclosporine A are added, which have been shown to improve remission rates. In more complex situations, characterized by resistance to conventional treatments, rituximab — an anti-CD20 monoclonal antibody — can be a valid therapeutic option.
When pure red cell aplasia is secondary to a thymoma, surgical resection of the tumor is the mainstay of therapy. In many cases, thymoma removal can induce spontaneous hematologic remission; however, in inoperable cases or if cytopenia persists after surgery, additional immunosuppressive therapy is necessary.
If the aplasia results from Parvovirus B19 infection, treatment consists of administering high-dose intravenous immunoglobulins (IVIG), particularly in immunosuppressed patients or those with persistent infections. This therapy neutralizes the virus and gradually restores erythropoiesis.
Regardless of the underlying cause, appropriate transfusion support is often necessary in the initial phases or in severe cases. Red blood cell concentrate transfusions aim to maintain hemoglobin levels compatible with adequate tissue oxygenation, minimizing the risk of organ ischemia. Close clinical monitoring is essential for the early detection of infectious, thrombotic, or immunosuppression-related complications.
The prognosis of pure red cell aplasia is generally favorable, especially when diagnosis is made early and treatment is prompt and adequate. However, the outcome strongly depends on the underlying cause and the individual response to immunosuppressive therapies.
Idiopathic forms respond positively in 50–70% of cases to steroid therapy or a combination with immunosuppressants. In infectious forms due to Parvovirus B19, early treatment with immunoglobulins often leads to complete remission. Forms associated with thymoma show more variable prognosis: even after surgical resection, erythroid suppression may persist or recur, necessitating long-term follow-up.
The main complications of pure red cell aplasia stem from severe anemia and the side effects of immunosuppressive therapies. The most significant include:
Opportunistic infections, favored by immune suppression, can be life-threatening especially in patients treated with aggressive immunosuppressive regimens or rituximab. Long-term transfusion dependence exposes patients to the risk of secondary hemosiderosis, with iron accumulation in vital organs, sometimes requiring iron chelation therapy. Also important is the risk of disease recurrence, which may occur upon withdrawal of immunosuppressive therapy, requiring further treatment cycles.
Finally, although rare, the risk of clonal evolution toward myelodysplastic syndromes or, more rarely, acute leukemias must be considered, making prolonged hematologic monitoring essential.