Pathophysiology of Intraepidermal Autoimmune Blistering Diseases
Light microscopic exam of the epidermis reveals small intercellular bridges or spines that connect the cells in the spinous cell layer. These spines are desmosomes that mediate cell-cell attachment and provide resistance to mechanical stress by connecting the cytoskeleton of adjacent cells. Antibodies against desmosome components at the spinous cell surface cause the acantholysis that defines pemphigus.
Desmosomes are composed of multiple proteins that can be divided into two functional groups: the transmembrane proteins and the plakin proteins. The transmembrane proteins are the desmogleins and the desmocollins. These proteins extend from the cytoplasmic desmosomal plaque, through the plasma membrane, and into the extracellular space. The plakin proteins make up the cytoplasmic attachment plaque into which keratin intermediate filaments of the cytoskeleton insert. The desmosomal plaque proteins include desmoplakin, plakoglobin, envoplakin, and periplakin.