A few rare genetic mutations, including variants in the tumor suppressor gene BRCA2, the DNA repair genes PALB2, BRIP1, CHEK2, and NBS1, and the transcription factor gene HOXB13, appear to confer a "moderate" excess risk of prostate cancer, and 76 common variants that confer a "small" excess risk have been identified by genome-wide association studies thus far, together explaining approximately 30 % of the familial risk of prostate cancer [42]. The gene discussed is CHEK2; the disease is prostate cancer.