Pure red-cell aplasia as the presenting feature of the carcionoid tumor of the thymus: case report

Acquired pure red-cell aplasia (PRCA) is an uncommon disorder of erythrocytopoiesis that can develop in association with thymic tumors. We present the very rare case of a severely anemic 62-year-old man with PRCA and a concurrent neuroendocrine carcinoid tumor of the thymus. The anterior mediastinal thymus tumor was completely excised, and following histological and immunohistochemical analyses (showing positive staining for cytokeratin, chromogranin A, synaptophysin, and neuron-specific enolase) the diagnosis of a (grade I; T₁N₀M₀) typical carcinoid tumor of the thymus was made. Postoperatively the anemia persisted despite no signs of residual tumor on CT chest. A hematological work up found: normocellularity with <0.5% erythroblasts and preserved megakaryocytopoiesis and granulocytopoiesis in a trephine biopsy; reduced numbers of Colony Forming Unit Erythroid (CFU-E) and normal numbers of Burst-Forming Unit Erythroid (BFU-E) in bone marrow colony-forming assays; a markedly increased level of serum erythropoietin; normal T and B-cell numbers with a normal CD4/CD8 ratio; and no clonal T-cell receptor -γ and -δ gene rearrangement) The patient responded favorably to a therapeutic trial of glucocorticoid immunosuppressive treatment (prednisone 1 mg/kg/day) with a normalization of the reticulocyte count and hematocrit, suggesting an immunologic mechanism for the PRCA. Though the exact mechanisms underlying the association between the PRCA and the carcinoid tumor of the thymus remain unknown.