We report a case in which metastatic castration-sensitive prostate cancer directly transformed into neuroendocrine prostate cancer without a corresponding increase in prostate-specific antigen.<h4>Case presentation</h4>An 86-year-old male with severe acute renal failure demonstrated a prostate-specific antigen level of 306 ng/mL and a Gleason score of 4 + 5 on prostate biopsy. This evidence concerns the gene KLK3 and Familial prostate cancer.