In the patients affected by CEP and PCT the expression levels of DBP and NFIL3 were significantly higher with regard to the patients affected by AIP, while significantly lower expression levels of ARNTL, CLOCK, CRY1, CRY2, CSNK1E, DBP NFIL3, NR1D1, PER2, and SIRT1 were found in symptomatic patients when compared to asymptomatic patients. This evidence concerns the gene PER2 and Congenital erythropoietic porphyria.