 1 BRCA1 or BRCA2 mutation, ATM deficiency, MRE11A mutation 2 Mutation of other HRhomologous recombination pathway genes: BLM, NBN, RAD50, RAD52, RAD54L, RAD51, RAD51B, RAD51C, RAD51D, RECQL, RECQL4, RECQL5, RPA1, WRN etc. 