This is a panepithelial disease of impaired cohesion due, at least in part, to a reduced number of desmosomes and defective gap junctions. Oral, nasal, vaginal, cervical, perineal, urethral, and bladder mucosa, in addition to external ocular surfaces, are involved. With exception of the ocular involvement, the lesions are usually not painful, but may be during acute flare-ups. Demarcated erythematous patches are often seen in the oral mucosa. Non-scarring alopecia, keratosis pilaris, and perineal intertrigo are usually present. Histological examination of oral mucosa and skin shows dyskeratotic features, decreased number of desmosomes, and intracytoplasmic vacuoles.