Felty Syndrome–Associated Clonal Cytotoxic T‐Cell Disease With Terminal Aggressive Progression: Shared STAT3 and TET2 Mutations Across a Prolonged Disease Course

Introduction: Biological overlap between Felty syndrome (FS) and clonal cytotoxic T-cell disorders is increasingly recognized, but aggressive progression is uncommon. Methods: We investigated an autopsy-confirmed case of terminal aggressive clonal T-cell disease that developed after a 4-year clinical course diagnosed as FS using serial immunophenotypic and molecular analyses. Results: mutations, and a newly emergent complex karyotype supported clonal continuity and terminal aggressive progression. Conclusion: This case provides clinicopathological evidence of long-term evolution in FS-associated clonal cytotoxic T-cell disease. Trial Registration: The authors have confirmed clinical trial registration is not needed for this submission.