#00066505

A 44-year-old man presented with dyspnea, dry cough, ecchymoses, and a 10-kg weight loss. He was pancytopenic (white blood cell count, 2.03 × 10⁹/L; hemoglobin, 6.5 g/dL; platelet count, 13 × 10⁹/L). Bone marrow showed near-complete aplasia with scattered lymphocytes, macrophages, and stromal cells (panel A, original magnification ×400, hematoxylin and eosin [H&E] stain). Computed tomography showed an anterior mediastinal mass consistent with thymoma (panel B). Pathologic evaluation after thymectomy confirmed thymoma (mixed type A/B; panel C, original magnification ×200, H&E stain). Evaluation for viral infections, autoimmune disease, paroxysmal nocturnal hemoglobinuria, and inherited marrow failure was negative. Lymphocyte subsets showed B-cell lymphopenia (CD19⁺ lymphocyte count below linear range), hypogammaglobulinemia (immunoglobulin A [IgA], 24 mg/dL; IgG, 374 mg/dL; and IgM, 12 mg/dL), and impaired T-cell proliferation (mitogen stimulation). The patient was diagnosed with aplastic anemia and Good syndrome (an acquired immunodeficiency characterized by thymoma and combined B- and T-cell dysfunction).

Thymoma is commonly associated with pure red cell aplasia; this case highlights its less recognized association with aplastic anemia and underscores the need for immune evaluation. The patient was treated with an allogeneic hematopoietic stem cell transplant using a 10/10 HLA-matched sibling donor, after conditioning with cyclophosphamide/antithymocyte globulin, and graft-versus-host disease prophylaxis with cyclosporine and methotrexate. As of this writing, he is at day 100 and has achieved donor engraftment with full donor chimerism.

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