Langerhans-cell degeneration in X-linked dominant ichthyosis. A quantitative and ultrastructural study

X-Linked dominant ichthyosis is a rare disorder of keratinization and represents a cutaneous hallmark of a distinct type of chondrodysplasia punctata [4]. Clinically, this type of keratinization disorder gives rise to ichthyosiform erythroderma in the newborn, and mild scaling with follicular atrophoderma in older children. We have recently demonstrated that, in Xlinked dominant ichthyosis, the slightly thinner epidermis displays characteristic ultrastructural features, including vacuolization of the granular cell layer and regular keratohyalin formation [6]. As an incidental finding, alterations of the epidermal Langerhans cells were noted. This prompted us to reexamine the behaviour of Langerhans cells in this rare ichthyosis using ultrastructural and quantitative methods. The study was performed on biopsies obtained from a 4-week-old baby and a 14-year-old girl who both showed the typical signs and symptoms of Xlinked dominant chondrodysplasia punctata [5]. The biopsies were taken from ichthyotic areas of the upper trunk and were processed by routine methods for electron microscopy. The numerical density of the epidermal Langerhans cells was evaluated directly by electron-microscopic examination of ultrathin sections. For this purpose, ultrathin sections of tissue blocks stained with lead citrate and uranyl acetate were mounted on Formvar-coated 50-mesh grids, and all of the epidermal Langerhans cells within one grid square were counted. Subsequently, the evaluated square was recorded on a 35-mm film in order to determine the epidermal surface within this square