Pure red cell aplasia associated with thymic follicular lymphoid hyperplasia: Complete remission after thymectomy without immunosuppression

Abstract

Abstract Background: Pure red cell aplasia (PRCA) is a rare hematologic disorder characterized by severe anemia, reticulocytopenia, and selective absence of erythroid precursors in bone marrow. While thymic neoplasms account for 10-15% of secondary PRCA cases, thymic follicular lymphoid hyperplasia (TFLH) is an exceptionally rare etiology, with approximately six cases reported in the medical literature since Wong et al. first described this association in 1995. Recognizing PRCA with a thymic origin is crucial, as it may represent a reversible cause of bone marrow failure. We report a case that demonstrates complete and sustained remission following thymectomy alone —challenging current treatment paradigms and suggesting an alternative therapeutic pathway. Methods: A 44-year-old previously healthy Thai male presented with progressive fatigue for one month. Physical examination revealed marked pallor without lymphadenopathy or hepatosplenomegaly. Laboratory studies showed severe normocytic anemia (hemoglobin 5.3 g/dL), striking reticulocytopenia (0.3%, absolute count 7,170/µL), normal white cell count (5,600/µL), and platelets (420,000/µL). Bone marrow examination demonstrated hypercellularity (90%) with normal granulocytic and megakaryocytic lineages but profound erythroid hypoplasia (<1%). Serological tests (HBsAg, anti-HCV, anti-HIV) were negative. Contrast-enhanced CT identified a 2.0 × 1.8 × 2.8 cm lobulated mass in the anterior mediastinum. Results: The patient underwent video-assisted thoracoscopic thymectomy. Histopathologic examination showed thymic tissue with prominent mature lymphoid proliferation in a follicular growth pattern, with an absence of thymocytes in affected areas and no significant expansion of thymic epithelial cells. The lymphoid follicles were rich in mature B cells exhibiting a typical germinal center phenotype, consistent with TFLH. Notably, hematologic recovery occurred spontaneously following thymectomy without immunosuppressive therapy. By two weeks, hemoglobin increased to 7.77 g/dL with reticulocyte count rising to 229,100/µL. Complete hematologic remission (hemoglobin 12.87 g/dL) was achieved by one month with a sustained response at four months of follow-up. Discussion: This case highlights several clinically significant findings. First, complete remission occurred without immunosuppressive therapy, aligning with a small number of previous reports in which thymectomy alone led to recovery. To date, only four such cases have been documented, making this the fifth case in which thymectomy alone led to complete remission, thereby strengthening the evidence supporting surgical intervention as a definitive therapy in selected patients. Second, the rapid hematologic recovery—within two weeks—suggests a direct pathogenic link between TFLH and erythroid suppression, most likely mediated by autoreactive T cells. Third, the case underscores the diagnostic challenge of distinguishing TFLH from thymoma preoperatively, emphasizing the essential role of histopathological confirmation. Conclusion: TFLH is a rare but potentially curable cause of secondary PRCA. Our case reinforces the growing body of evidence that thymectomy alone may lead to complete remission, even without immunosuppression. This approach may offer significant clinical and economic advantages, particularly in resource-limited settings. Timely evaluation of mediastinal pathology in unexplained PRCA is essential to avoid unnecessary immunosuppressive therapy. Further studies are warranted to identify predictive markers of response and to refine criteria for patient selection for this surgical strategy.