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. Here, BRCA1 is linked to hypoparathyroidism-retardation-dysmorphism syndrome.