A specific defect in glycosylation of epidermal cell membranes. Definition in skin from patients with epidermolysis bullosa simplex.

Why blister formation occurs within the epidermis in epidermolysis bullosa (EB) simplex is not known. One possibility is that there are diminished amounts, absence, or biochemical alterations of one or more structural components of epidermal cell membranes, thereby leading to increased skin fragility. In order to test this hypothesis, biopsy specimens were obtained from clinically normal-appearing skin of patients with simplex, junctional, and dystrophic forms of EB and normal adult volunteers. Immunofluorescence studies were performed on each specimen using eight fluorescein-labeled affinity-purified lectins shown to bind uniformly to epidermal cell membranes of normal human adult skin and neonatal foreskin. To examine the epidermal cytoskeleton, each tissue specimen was also examined using two antikeratin monoclonal antibodies. Irregular and focally granular epidermal membrane staining was noted in each EB simplex specimen examined with the lectin-peanut agglutinin. In contrast, uniformly crisp membrane staining was seen in each specimen from patients with junctional or dystrophic EB and from normal volunteers. This epidermal cell membrane glycosylation defect appears to have the restricted carbohydrate specificity of peanut agglutinin since staining of EB simplex skin with each of the remaining seven lectins was indistinguishable from that seen in skin from patients with the other forms of EB and normal adult skin. Furthermore, the epidermis in EB simplex skin appears to be selectively abnormal since the same tissue specimens demonstrated normal keratin cytoskeleton staining.