Pachydermia

PACHYDERMIA, pachydermia (from Greek pachys-thick and derma-skin), a pathological condition of the skin or mucous membranes, characterized by marked thickening and hardening. P. sometimes develops on the basis of congenital predisposition, but more often has an acquired character and is the result of the effect on the skin (or mucous membranes) of various chronic inflammations or mechanical and professional irritations. The basis of P. is either thickening of the epithelial covering itself or a corresponding change in connective tissue. In the first case, P. develops due to excessive keratinization of the epidermis (hyperkeratosis), which occurs in numerous skin diseases, or as a result of the metaplastic transformation of non-keratinizing epithelium into keratinizing epithelium, which is observed in some chronic inflammations and irritations. An example of this type of P. can be the thickening of the epithelium of the vaginal mucosa in uterine prolapse or the proliferation and marked thickening of the epithelium with keratinization (epidermoidal transformation), which occurs on the true vocal cords in chronic laryngitis and is known as pachydermia laryngis diffusa. The epithelium in this case has a bluish or milky-white appearance and sharply contrasts with the surrounding hyperemic tissue. Sometimes the thickened epithelium is located on a papillary proliferated stroma; then they speak of pachydermia laryngis verrucosa. Another type of P., developing due to thickening of the skin's connective tissue, develops on the basis of chronic inflammation of the lymphatic vessels or due to their prolonged dilation and stagnation of lymph due to impaired outflow (in the case of obliteration or complete removal of regional lymph nodes). In such cases, edematous infiltration and hyperplasia of the skin's connective tissue develop, designated as pachydermia lymphangiectatica, for example, on the arm after removal of the axillary glands (in cancer of the breast gland), on the leg in a suppurating bubo, in chronic ulcers of the leg, both non-specific and tuberculous or syphilitic (cases associated with varicose veins are designated pachydermia phlebectatica). A higher degree of hyperplasia of connective tissue, reaching tumor-like dimensions, is known under the name elephantiasis (see Elephantiasis). All the described forms of P. do not undergo reverse development.