Recent studies suggest that KMT2D insufficiency in T-cells may be disruptive as researchers have identified KMT2D mutations in 20% of peripheral T-cell lymphomas-not otherwise specified (PTCL NOS), a disease with notable T-cell dysfunction tied to dysregulated expression of the cell cycle and adhesion genes (7, 8). This evidence concerns the gene KMT2D and peripheral T-cell lymphoma, not otherwise specified.