The structure and function of dermal connective tissue in normal individuals and patients with inherited connective tissue disorders.

Normal, human dermis is a dense, interwoven collagen and elastic matrix organized into papillary and reticular regions. the papillary dermis is a narrow zone beneath the epidermis which includes an even narrower subepidermal connective tissue band beneath the basal lamina. The reticular dermis has superficial intermediate and deep reticular zones. Each region is distinguished by the organization of the fibrous connective tissue. In this review, the structure, composition and function of each region of the normal dermis is surveyed and alterations in the tissue that have been recognized ultrastructurally in skin from patients with inherited connective tissue diseases are discussed. A molecular defect in a connective tissue molecule can be expressed phenotypically at one or more levels of dermal organization and can modify the structure of other matrix components. In some cases, the entire interwoven pattern of the dermis is altered; in others, the dermis retains the interwoven pattern and alterations are expressed as defects in the association of fibrils into fibers and fiber bundles. Abnormalities in the size, packing and relationships of fiber bundles also can occur. These changes involve the collagen matrix primarily. Depletion or exaggeration of elastin, or of the amorphous ground substance can also influence the organization of collagen and of the overall dermal architecture. The alterations described are illustrated with scanning electron micrographs of skin from patients with inherited connective disorders and are discussed in terms of the mechanical abnormalities of the tissue.