For example, individuals with homologous recombination deficiency (HRD) due to BRCA mutations may benefit from PARP inhibitors (Mirza et al., 2016), while coexisting mismatch repair (MMR) deficiency (e.g., MSH2, PMS2) may make them eligible for immunotherapy (Le et al., 2017). Here, MSH2 is linked to hypoparathyroidism-retardation-dysmorphism syndrome.