As demonstrated in our companion paper, the etiological basis of HRD was, however, only identifiable in 16% of these cases based on biallelic inactivation of BRCA1, BRCA2, PALB2, BRIP1 or RAD51B through germline and somatic mutations29. This evidence concerns the gene RAD51B and hypoparathyroidism-retardation-dysmorphism syndrome.