_[-2]proPSA and Prostate Health Index (PHI; Beckman Coulter Inc., Brea, CA, USA): a combination of blood tPSA and isoforms of fPSA deriving from the incomplete removal of a peptide chain from the precursor molecule of the PSA, in 2012 received Food and Drug Administration (FDA) approval for the discrimination of PC versus prostate benign conditions. Here, KLK3 is linked to pachyonychia congenita.