PSA (human kallikrein 3) is a serine protease, and it is almost exclusively secreted by prostate epithelial cells, and it is used to detect prostate cancer in asymptomatic individuals over 50 years, people over 40 years with a family history of prostate cancer, and those who come with prostatism symptoms (2). The gene discussed is KLK3; the disease is Familial prostate cancer.