Thus, COL5A3, COL6A6, and MMP9 are important for the collagen formation [145,146,147]; KDR, one of the two receptors of the VEGF, has been associated with integrin cell surface interactions with extracellular matrix [148]; mutations in STS (steroid sulfatase) have been associated to X-linked ichthyosis [148]; rare variants of MCM10, a key component of the pre-replication complex, have been described for the first time associated to AD [81]. The gene discussed is MMP9; the disease is syndromic recessive X-linked ichthyosis.