BRCA1 and hypoparathyroidism-retardation-dysmorphism syndrome: A significant difference in BRCA1 promoter methylation was observed between the HRD and HRP groups (P value < 0.01), with BRCA1 promoter methylation detected in 56.25% (9/16) of HRD patients and in none of the HRP patients (Fig. 5B).