CYP3A4 and pure red-cell aplasia: Moreover, we found that the frequency of CYP3A4*1B and VDR TT combined genotypes is increased in BPH patients who developed PRCa later on in their life compared with BPH patients who did not, and the risk of developing PRCa was 13-fold higher in BPH patients having the CYP3A4*1B and VDR TT combined genotypes than the control (Tayeb et al, 2002, submitted).