by Sarah Brenner, MD, Jacob Mashiah, MD, Einat Tamir, MD, Ilan Goldberg, MD and Yonit Wohl, MD, Department of Dermatology, Tel Aviv Sourasky Medical Center, and Sackler Faculty of Medicine, Tel Aviv University, Israel
Pemphigus is generally considered to stem from a genetic predisposition to the disease triggered and/or aggravated by one or more external factors. An acronym has been suggested from the name of the disease, PEMPHIGUS, to encompass those factors:
Gardening materials and pesticides are a major group of agents implicated in the development of the disease. The medical literature documents numerous cases provoked by pesticides all over the world. Organochlorine pesticides, and organophosphates, a new generation of pesticides, have been tied to the disease.
How pesticides work on the skin is unclear. It is speculated that the immune system is activated via contact or systemic exposure, resulting in the generation of autoantibodies targeting desmosomal antigens. Interestingly, in most of the reported cases the patients had a first-time, long-duration exposure to the offending substance, and developed the disease only after a massive additional exposure, resembling the induction and elicitation phases of allergic contact dermatitis.
Pemphigus has been associated with malignant processes, mainly hematolymphoproliferative diseases such as Hodgkin's lymphoma, chronic lymphocytic leukemia, Castelman's disease, and others. These constitute a specific clinicopathological variant called paraneoplastic pemphigus. A few reports on cases of pemphigus associated with malignant diseases that did not meet the above criteria raised the possibility of simple co-existence. In both events, the physician should perform a malignancy-directed work-up on a pemphigus patient.
Drugs reported to induce pemphigus are divided into three main groups according to their chemical structure: drugs containing a sulfhydryl radical such as penicillamine; phenols such as rifampin, levodopa and aspirin; and nonthiol nonphenol drugs, such as calcium channel blockers, angiotensin converting enzyme inhibitors, NSAIDS, dipyrone, and glibenclamide.
Again, speculated mechanisms are chemical insult and immune system activation by a complicated mechanism involving diverse molecules (autoantibodies, cytokines). Calcium channel blockers are emphasized in view of the fact that the calcium ion is critical to maintaining an intact epithelium.
Pregnancy is closely related to autoimmune diseases and thus to immunoblistering diseases, an association seen in the aggravation of pemphigus vulgaris during pregnancy, and pregnancy- or postnatally-induced herpes gestationis and neonatal pemphigus. These diseases are attributed to the passage of pathogenic autoantibodies via the placenta that target different placental antigens or skin antigens in the newborn. The role of sex hormones, mainly estrogen, in the pathogenesis of pemphigus has not yet been established.
Different infectious agents and immunizations can induce or exacerbate pemhigus, mainly by activating the cellular immune system. The most frequently incriminated infectious agents are the viruses of the herpetoviridae family, namely herpes simplex, EBV, CMV, and even HH8.
Despite the confusing clinical similarities of viral diseases and pemphigus, and because of the different outcomes of the two conditions, it is important to diagnose viral infection in a pemphigus patient and initiate early antiviral therapy, often as an adjunct to immunosuppressive therapy. Viral isolation remains the most reliable laboratory means for viral diagnosis, followed by molecular biology techniques, which are more sensitive but less reliable and indicated only in cases in which the results of the former are not conclusive.
In addition, bacteria such as coagulase positive staph aureus are capable of inducing pemphigus. Gram negative bacteria and even Actinomyces have been cultured in patients before the pemphigus becomes manifest, and were therefore described as its possible triggers.
Although rarely mentioned in the literature, recent studies indicate that certain foods can induce or trigger pemphigus. Some nutritional components are chemically similar to known causative drugs, and may act in the same way. The following chemicals and related foodstuffs have been associated with pemphigus:
Fruits: mango, bananas, potatoes, tomatoes
Nuts: pistachio, cashew
Pinenes: baked goods, smoked and grilled food, candy, chewing gum, ice cream, black pepper
Food additives: aspartame, sodium benzoate, tartrazine, vanillin, eugenol, caffeic acid, cinnamic acid, vitamis C and E
Nuts: Kola, betal, walnuts
Fruits: cassava, cranberry, raspberry, blackberry, cherry, banana, apple, pear, grape skins, peach avocado
Drinks: tea, mate, fruit juice, beer, wine, liquors, water, coffee, guarana
Food additives: vanillin
Spices: ajowan, coriander, cumin, black pepper, red chilies, rosemary, garlic, ginger
Vegetables: garlic, onion, shallot, chive, leek
Assuming that foods containing thiol, phenol, and polyphenolic compounds may contribute to pemphigus, avoidance of certain foods may lead to remission.
Pemphigus is considered a photosensitive disease, especially the superficial variant pemphigus erythematosus. Ultraviolet radiation, either occupation- or leisure-related, can induce or exacerbate the clinical manifestation. Whether the phototoxic reaction is a simple one or entails specific immune system stimulation remains to be determined.
Physical factors such as x- ray radiotherapy, burns, major surgery and cosmetic procedures have also been reported capable of inducing pemphigus.
The well-known connection between the immune and nervous systems raises the possibility that a psychoneural disorder can influence the onset and course of autoimmune disease. Several studies and case reports point to the possible contribution of emotional stress as a precipitating factor in pemphigus. Hence, avoiding emotional stress may be therapeutic in pemphigus patients, hastening the healing process and reducing or stopping the use of immunosuppressive drugs.
In summary, while the myriad causes of pemphigus complicate the differential diagnosis and course of the disease, it also points to the numerous factors that can help in its diagnosis and treatment. These factors have been documented in the studies cited here. The acronym is suggested to give clinicians a tool to pinpoint possible causes and prevent flare-ups in every newly diagnosed pemphigus patient.