Gluud et al. (2023) provided evidence that malignant T cells in CTCL secrete cytokines IL-13, IL-22, and oncostatin M (OSM) to induce JAK-STAT signaling in the surrounding keratinocytes; downregulate the filaggrin expression; and impair the skin barrier function [10]. This evidence concerns the gene OSM and primary cutaneous T-cell non-Hodgkin lymphoma.