In some cases of pemphigus (pemphigus vegetans) a vegetating or papillomatous condition develops from the base of the lesion, with an offensive discharge; it is usually a grave type of the malady. Exceptionally cases (dermatitis vegetans) are met with which have a close similarity in their symptoms to pemphigus vegetans, but in which the eruption is more or less limited to the genitocrural region. The disorder is not malignant and usually yields to cleanliness and antiseptics. #What is the character of the subjective symptoms in pemphigus?# The subjective symptoms consist variously of heat, tenderness, pain, burning and itching, and may be slight or troublesome. #What is known in regard to the etiology of pemphigus?# The causes are obscure; general debility, overwork, shock, nervous exhaustion, and septic conditions (microorganisms) are thought to be of influence. There seems no doubt that those who have to do with cattle products, especially butchers, are subjects of acute and usually grave pemphigus. Vaccination has exceptionally been responsible for the disease, probably through some coincidental infection. The disease is not contagious, nor is it due to syphilis. It may occur at any age. It is a rare disease, especially in this country. Most of the cases diagnosed as pemphigus by the inexperienced are examples of bullous urticaria, bullous erythema multiforme, and impetigo contagiosa. #What is the pathology?# The lesions are superficially seated, usually between the horny layer and upper part of the rete. Round-cell infiltration and dilated blood vessels are found about the papillae and in the subcutaneous tissue. The contents of the blebs, always of alkaline reaction, are at first serous, later containing blood corpuscles, pus, fatty-acid crystals, epithelial cells, and occasionally uric acid crystals and free ammonia. #From what diseases is pemphigus to be differentiated?# From herpes iris, the bullous syphiloderm, impetigo contagiosa and dermatitis herpetiformis. #How do these several diseases differ from pemphigus?# The acute course, small lesions, concentric arrangement, variegated colors, and distribution, in herpes iris; the thick, bulky, greenish crusts, the underlying ulceration, the course, history, and the presence of concomitant symptoms of syphilis, in the bullous syphiloderm; the history, course, distribution, the character of the crusting, and the contagious and auto-inoculable properties of the contents of the lesions, in impetigo contagiosa; the tendency to appear in groups, the smaller lesions, the intense itchiness, course, multiform characters of the eruption and the disposition to change of type in dermatitis herpetiformis,--will serve as differential points. #State the prognosis of pemphigus.# Its duration is uncertain, and the issue may in severe cases be fatal. In the milder types, after months or several years, recovery may take place.