MDS precursors evidence cell swelling, a pyroptotic hallmark. (A) Mean cell area was quantified from confocal images of BM-MNCs from normal donors (n = 6) vs MDS patient specimens (n = 7 lower risk, n = 3 higher risk). (B) Flow cytometric analysis of mean SSC-A intensity of BM-MNCs isolated from normal donors (n = 6) or LR-MDS patients (n = 7). MDS BM-MNCs have mean cell area that is 2.0-fold greater than ungated BM-MNCs (P = .017), 2.2-fold greater than stem cells (CD34⁺CD38⁻; P = .019), 1.5-fold greater than progenitor cells (CD34⁺CD38⁺), 1.6-fold greater than immature myeloid progenitors (CD33⁺), and 2.0-fold greater than erythroid progenitors (CD71+; P = .038). (C) NLRP3 MFI correlates with BM-MNC area in LR-MDS patients (r = 0.49, n = 7). (D) EtBr dye incorporation in BM-MNCs from normal donors (n = 3) and MDS patients (n = 3) was measured at 5-minute intervals by flow cytometry. (E, left to right) Photomicrograph images from normal donors illustrating normal red blood cell (RBC; 7.0 μm) followed by normal erythroid lineage maturation of nucleated BM precursors with corresponding cell diameter. (F) Corresponding images from MDS BM aspirates, demonstrating an oval macrocyte (RBC, 9.1 μm) followed by dysplastic and megaloblastic erythroid lineage maturation. (G) Normal myelocyte. (H) Enlarged dysplastic myelocyte with mild hypogranulation in MDS. (I-J) Erythroid (I) and myeloid (J) lineage maturation comparison of mean cell diameter in BM of normal donors (n = 4) vs MDS patients (n = 4). Maturation is depicted as most to least mature cell populations from left to right. Error bars represent SE. *P < .05, ** P < .01, and ***P < .001.