From a patient who progressed from RUNX1-FPD (expressing mtRUNX1 K194N) to FPD-MM, with co-mutations documented by NGS in BCOR, PHF6, SF3B1 and SRSF2, we procured BMA cells and successfully established the first, continuously cultured cell line (GMR-AML1) expressing the same germline mtRUNX1. The gene discussed is SF3B1; the disease is Miyoshi myopathy.