by Luis A. Diaz, M.D.
Professor and Chairman Department of Dermatology Medical College of Wisconsin
Milwaukee, Wisconsin
Pemphigus foliaceous (PF) one of the major clinical variants of pemphigus, is characterized by superficial blisters and anti-epidermal autoantibodies. The epidermal antigen with which PF autoantibodies react is a desmosomal protein designated desmoglein 1 (dsg1). There are two forms of PF-a sporadic form which has worldwide distribution, and an endemic form, which has only been observed in certain rural areas of Brazil, Columbia and Tunisia.
by Luis A. Diaz, M.D. Professor and Chairman Department of Dermatology Medical College of Wisconsin Milwaukee, Wisconsin
Pemphigus foliaceous (PF) one of the major clinical variants of pemphigus, is characterized by superficial blisters and anti-epidermal autoantibodies. The epidermal antigen with which PF autoantibodies react is a desmosomal protein designated desmoglein 1 (dsg1). There are two forms of PF-a sporadic form which has worldwide distribution, and an endemic form, which has only been observed in certain rural areas of Brazil, Columbia and Tunisia.
In Brazil, the endemic form of PF is known as Fogo Selvagem. The name FS translates to "wildfire" in Portuguese and refers to the burning sensation that the patients feel upon sunlight exposure. The endemic and non-endemic forms of PF exhibit indistinguishable clinical, histological and immunological characteristics, i.e., superficial blistering caused by autoantibody-mediated cell-cell detachment within the outer layers of the epidermis.
In summary, FS is a human autoimmune disease mediated by pathogenic autoantibodies that are produced by immunogenetically predisposed individuals living in certain rural areas of Brazil. The results of epidemiological studies of FS point toward a, as yet unknown environmental antigen as the trigger of the disease.
The antigenic mimicry model predicts that the dsg1 protein harbors T and/or B cell epitopes that are shared with the environmental agent that precipitates the disease. We have recently identified a new FS focus with a unique set of environmental, genetic and cultural characteristics that make it an ideal population on which to focus our investigations on the epidemiology and etiology of this disease. This community, the Limao Verde Indian Reservation in central Brazil, is composed of approximately 1000 members of the Terena Indian Tribe. Geographic, familial and temporal clustering patterns have been detected among the 31 FS cases on this reservation, and the disease was found to be associated with HLA-DRB180404, 1402 & 1406 haplotypes (RR=14).
In contrast, other Terena reservations in the region show very few or no documented FS cases. We are currently carrying out a series of case control epidemiological studies designed to further define genetic and environmental risk factors of the disease. Controls from three populations will be studied: unaffected family members of FS patients, unrelated individuals from Limao Verde, and unaffected Terena Indians from a neighboring reservation.
Other ongoing studies include the following: a) a prospective sero-epidemiological survey of this population using indirect immunofluorescence and an ELISA assay with recombinant dsg1; and b) investigations of the cellular and molecular regulatory mechanisms involved in the pathogenic autoimmune response in these patients. Information obtained from these studies would be relevant in understanding the onset and development of FS and other human autoimmune diseases.
