In detail, the level of MMP-2/-9/-13 degraded collagen type I (C1M) was 4-fold higher in PC patients as compared to controls and the levels of MMP-9 degraded collagen type III (C3M), MMP-9 degraded collagen type IV (C4M) and MMP-12 degraded collagen type IV (C4M12a1) were 2-fold higher in PC patients as compared to controls. This evidence concerns the gene MMP9 and pachyonychia congenita.