A case report of CD4- CD8+ CD56- TCRγδ+ T-large granular lymphocytic leukaemia with severe aplastic anemia and a PNH clone.

T-large granular lymphocytic leukemia (T-LGLL) is a rare, indolent lymphoproliferative disorder of lymphocytes. Clonal expansion of T cells, driven by dysregulation of Fas-mediated apoptosis following activation, is a hallmark of this disease. In recent years, research on large granular T-cell leukemia has grown substantially compared with the past; however, most reports have focused on TCRαβ+ cases, while studies on other subtypes remain limited, and diagnostic experience with coexisting conditions requires further refinement. This study reports, for the first time, a case of CD4- CD8+ CD56- TCRγδ+ T-LGLL complicated by severe aplastic anemia (AA) and a paroxysmal nocturnal hemoglobinuria (PNH) clone. The case is characterized by positive TCRγδ gene rearrangement, with T-cell-mediated hematopoietic suppression leading to the development of AA and the PNH clone. We hope this study will address a gap in the current literature. Here, we summarize the common pathophysiological mechanisms and guiding treatment principles for these three diseases.