Epidermolysis bullosa (EB) is a heterogeneous group of genetic bullous skin diseases. The EB simplex group (EBS) is characterized by intraepidermal blistering. EBS-Ogna was first described as a separate entity based on clinical studies. Later genetic linkage of EBS-Ogna to the GPT locus for glutamate pyruvate transaminase (alanine transaminase) was detected and GPT was assigned to chromosome 8, then to the terminal long arm band 8q24. Plectin is an abundant and widespread cytoskeletal protein which has been proposed as a general crosslinking element of intermediate filaments. Human plectin has recently been cloned and in situ hybridized to chromosome 8q24. To examine whether plectin could be associated with EBS-Ogna we performed an immunohistochemical study with a panel of mAbs to rat plectin. Interestingly, 2 of these mAbs showed strong intracellular staining of the suprabasal and basal layer of the epidermis in all control samples, whereas no reactivity of the basal layer was found in the Ogna group. These results strongly suggest that plectin is involved in the pathogenesis of EBS-Ogna.