FPD/AML pedigrees. Squares indicate male and circles indicate female. Open symbols represent unaffected persons, half-filled symbols represent persons affected by FPD, and closed symbols represent persons affected by FPD who developed acute leukemia. The letters A and B indicate that a germline RUNX1 mutation and an acquired RUNX1 alteration could have been identified, respectively. Person III-1 in pedigree 2 developed T-ALL and person II-2 in pedigree 3 developed T-ALL followed by AML 5 years later. Both are also denoted with a closed symbol.