Biomedical subjects
Publications and source records attributed to T Hermanns-Le.
Merkel cell carcinoma is a neuroendocrine tumor of the skin, originating from neuroendocrine cells. A case report of Merkel cell carcinoma, discovered in a 77-Year-old woman, was diagnosed and confirmed on a biopsy. Diagnostic and therapeutic orientations of this unusual but malignant tumor are described.
Classical Ehlers-Danlos syndrome (EDS) is characterized by skin hyperelasticity, joint hypermobility, increased tendency to bruise, and abnormal scarring. Mutations in type V collagen, a regulator of type I collagen fibrillogenesis, have been shown to underlie this type of EDS. However, to date, mutations have been found in only a limited number of patients, which suggests genetic heterogeneity. In this article, we report two unrelated patients with typical features of classical EDS, including excessive skin fragility, in whom we found an identical arginine-->cysteine substitution in type I collagen, localized at position 134 of the alpha1(I) collagen chain. The arginine residue is highly conserved and localized in the X position of the Gly-X-Y triplet. As a consequence, intermolecular disulfide bridges are formed, resulting in type I collagen aggregates, which are retained in the cells. Whereas substitutions of glycine residues in type I collagen invariably result in osteogenesis imperfecta, substitutions of nonglycine residues in type I collagen have not yet been associated with a human disease. In contrast, arginine-->cysteine substitutions in type II collagen have been identified in a variety of chondrodysplasias. Our findings show that mutations in other fibrillar collagens can be causally involved in classical EDS and point to genetic heterogeneity of this disorder.
Corneocyte desquamation at the skin surface is a complex biologic event which is normally regulated for providing an inconspicuous shedding of single corneocytes. When altered, the process gives rise to xerotic and ichthyotic conditions. The present review focusses on important biologic and molecular aspects responsible for normal and altered corneocyte desquamation. There is a complex relationship between epidermal cell production, maturation and desquamative loss. Corneocyte hydration, stratum corneum barrier function and enzymatic corneodesmolysis are involved in a dynamic interrelationship. Many physiological and environmental factors acting in a different time frame influence desquamation.