Metalloproteinase-9 (MMP-9) is involved in the pathogenesis of anti-p200 pemphigoid; at the same time, in patients with psoriasis, the overproduction of many cytokines results in increased expression of MMP-9, and this in turn may stimulate the degradation of laminins, which induces the production of autoantibodies. This evidence concerns the gene MMP9 and psoriasis.