CXCR4 and paroxysmal nocturnal hemoglobinuria: To determine whether or not the diminished CXCR4 expression on HSPCs was common to patients with escape clonal hematopoiesis, we studied PB HSPCs of five paroxysmal nocturnal hemoglobinuria (PNH) patients (PNH1–5) for whom both glycosylphosphatidylinositol (GPI)(−) and GPI(+) CD34+ cells were evaluable.