Upon quantifying the immunohistochemical reactions, we observed that the protein expression of the enzyme MMP9 was higher in the psoriasis plaque than the skin collected from the Non-affected area 154.69 ± 18.94 ou/μm2 versus 136.16 ± 22.92 ou/μm2 (p = 0.0311). This evidence concerns the gene MMP9 and psoriasis.