Connective tissue disorders affecting skin can be inherited or acquired and might result from an alteration of structure, function or metabolism of the constitutive elements of the supporting matrix. Collagen, the protein building the fibrous framework of the dermis, is considered as an example in understanding such a pathology at the molecular level. The molecular structure, the polymerizing capacity and the degradation of this large protein depends upon the activity of several specific post-transcriptional enzymes operating inside or outside of the cells. Pathology is known to be associated with an altered activity of most of these enzymes. Several pathological skin conditions are defined at the level of their molecular defect as in several types of the Ehlers-Danlos syndrome, osteogenesis imperfecta. Menkes' kinky hair disease, epidermolysis bullosa and scurvy. A similar molecular pathogenesis can be logically hypothesized for various other processes involving connective tissue as in scleroderma, pretibial myxoedema, cheloids, Werner syndrome, aging and corticosteroid induced atrophy.