RAD51C and hypoparathyroidism-retardation-dysmorphism syndrome: Inactivation through promoter methylation of BRCA1 and RAD51C has also been found to result in HRD tumors (Ruscito et al., 2014; Polak et al., 2017; Staaf et al., 2019), and these tumors also demonstrate increased sensitivity to PARPi and platinum (Kondrashova et al., 2018).