Mid-dermal elastolysis: an ultrastructural and biochemical study.

Mid-dermal elastolysis (MDE) is a particular elastic tissue disorder in which selective loss of elastic fibres occurs in the mid-dermis. It is clinically characterized by the appearance of fine wrinkling of the epidermis and perifollicular protrusion which gives the skin an aged appearance. It is sometimes associated with an inflammatory event such as urticaria while other cases are regarded as idiopathic. The pathogenesis of MDE is still obscure. Some authors have underlined the role of macrophage activation and others have imputed UV radiation. We report here a typical case of MDE arising after several attacks of solar urticaria. Electron microscopic and biochemical studies were carried out. Ultrastructural examination showed active elastophagocytosis by macrophages and mast cells, often degranulated, near phagocytosing cells. Biochemical studies demonstrated that fibroblasts derived from lesional skin of the MDE patient produced high levels of elastase and cathepsin G compared with fibroblasts from a healthy sex- and age-matched control. Phagocytosis of morphologically normal elastic tissue is a noticeable characteristic feature of MDE. In our case mast-cell activation and the abnormal synthesis and/or release of fibroblast elastolytic enzymes seemed to play a role in the pathogenesis of the MDE.