Pemphigus is a disease that causes blistering of the skin and the inside of the mouth, nose, throat, eyes, and genitals. The disease is rare in the United States. Pemphigus is an autoimmune disease in which the immune system mistakenly attacks cells in the top layer of the skin (epidermis) and the mucous membranes. People with the disease produce antibodies against desmogleins, proteins that bind skin cells to one another. When these bonds are disrupted, skin becomes fragile, and fluid can collect between its layers, forming blisters.