▪Reduced decidualized of an IGFBP1+ endometrial stromal cell subset in EM cases suggested impaired decidualization▪Endometrial stromal cells in EM exhibited pro-inflammatory and senescent characteristics▪Identification of a unique proliferating uNK cell subpopulation in controls, mostly absent in EM. Here, IGFBP1 is linked to erythema multiforme.