Cells with wild-type BRCA2 genes repair DNA DSBs through HR; however, cells with mutations in BRCA2 or those with homologous recombination deficiency (HRD) are susceptible to poly (ADP-ribose) polymerase (PARP) inhibitors, leading to synthetic lethality [15, 16]. Here, BRCA2 is linked to hypoparathyroidism-retardation-dysmorphism syndrome.