A single institution case series of 84 patients with CAH or FIGO grade 1 EC reported poor response to progestin treatment in patients with deficient MMR proteins (i.e., MLH1, MSH2, MSH6, and PMS2), but the deficient MMR cohort had only 6 patients, limiting the generalizability [98]. The gene discussed is MRC1; the disease is congenital adrenal hyperplasia.