The loss of function of BRCA1 or BRCA2 due to a pathogenic germline variant (PGV) in the BRCA1 or BRCA2 gene respectively can lead to homologous recombination deficiency (HRD), where a cell cannot rely on HR to efficiently repair double-stranded DNA breaks [2–4]. This evidence concerns the gene BRCA1 and hypoparathyroidism-retardation-dysmorphism syndrome.