Ultrastructural localization of cell junctional components (desmoglein, plakoglobin, E‐cadherin, and β‐catenin) in Hailey‐Hailey disease, Darier's disease, and pemphigus vulgaris

The distribution of desmoglein, plakoglobin, E‐cadherin, and β‐catenin in the peri‐lesional and lesional skin of Hailey‐Hailey disease, Darier's disease, and pemphigus vulgaris was examined by immunoelectron microscopy. In the peri‐lesional skin, the immunolabeling of these desmosomal components was localized to desmosomes. Adherens junction‐associated E‐cadherin and β‐catenin were at the cell periphery, excluding desmosomes. The labeling pattern was similar among these diseases, but the labeling intensity particularly that of plakoglobin in Hailey‐Hailey disease and Darier's disease, was less than that of normal controls, suggesting that these glycoproteins are quantitatively less concentrated in the normal epidermis of these inherited diseases. In the acantholytic cells of Hailey‐Hailey disease and Darier's disease the immunolabeling of the components of desmosomes was diffusely distributed in the cytoplasms, whereas that of adherens junction was mostly at the cell periphery and partly diffusely in the cytoplasm. In contrast, desmosomes of detaching keratinocytes in pemphigus vulgaris still showed the labeling of desmoglein and plakoglobin. These findings suggest that the inherited acantholytic diseases, i.e., Hailey‐Hailey disease and Darier's disease have a different pathogenesis from that of autoimmune acantholysis in pemphigus vulgaris: The intracellular components of desmosomes may primarily be disrupted in the genetic acantholytic diseases in the initial stages of acantholysis. Several unsolved questions in the previous light microscopic immunofluorescence sttidies using the same antibodies are now answered: 1) the diffusion of desmosomal proteins is not due to the internalization of desmosomes, 2) intracellular components of adherens junction are also finally dissolved, 3) diffuse cytoplasmic immunofluorescence patterns of desmosomal components could be explained by immunoelectron microscopy as those attached to cell membrane and trapped in tonofilament aggregates.