A comparative international cohort of germline RUNX1 variant carriers without and with hematological malignancies (HM) identified striking heterogeneity in rates of early-onset clonal hematopoiesis (CH), with a high prevalence of CH in RUNX1 carriers who did not have malignancies (carriers without HM). The gene discussed is RUNX1; the disease is cyclic hematopoiesis.