Found this part interesting, seems only one promoter gene for Type2 5AR shows signs of methylation and that occurs in tissue only and not in blood of CSF fluid. Also there is no signs of methylation for Type1 promoter.
Epigenetic modifications seem to be also involved (Melcangi et al., 2019). Indeed, as recently demonstrated, methylation analysis of the promoter genes coding for type 1 (i.e., SRD5A1 ) and type 2 (i.e., SRD5A2 ) 5α-R performed in plasma and CSF of 16 PFS patients, indicated that SRD5A2 promoter was more frequently methylated in CSF of PFS patients compared to healthy controls (56.3% versus 7.7%). **Importantly, this is a tissue-specific methylation. Indeed, SRD5A2 promoter methylation has not been observed in plasma. Interestingly, both in plasma and CSF, SRD5A1 promoter was not methylated ([Melcangi et al., 2019]**(https://www.sciencedirect.com/science/article/pii/S235228951930061X#bib69)).