Pathogenic/likely pathogenic (P/LP) germline variants in RUNX1 cause familial platelet disorder with associated myeloid malignancies (FPDMM), also known as RUNX1-Familial Platelet Disorder (RUNX1-FPD, or FPD), a condition characterized by qualitative and quantitative platelet defects and predisposition to hematopoietic malignancies. The gene discussed is RUNX1; the disease is hereditary thrombocytopenia and hematological cancer predisposition syndrome associated with RUNX1.