Fogo selvagem: endemic pemphigus foliaceus

Abstract

Fogo selvagem or endemic pemphigus foliaceus is an autoimmune acantholytic anti-cadherin bullous disease that primarily affects seborrheic areas, which might disseminate. Brazil has the world's largest number of patients, mainly in the Central-West region, but the disease has also been reported in other South American countries. It affects young people and adults who have been exposed to rural areas, with occurrence of familial cases. Anti-desmoglein-1 autoantibodies are directed against desmosomal structures, with loss of adhesion of the upper layers of the epidermis, causing superficial blisters. The etiology is multifactorial and includes genetic, immune, and environmental factors, highlighting hematophagous insect bites; drug-related factors are occasionally involved. Flaccid blisters readily rupture to yield erosive-crusty lesions that sometimes resemble seborrheic dermatitis, actinic keratosis, and chronic cutaneous lupus erythematosus. The clinical presentation varies from localized to disseminated lesions. Clinical suspicion should be confirmed with histopathological and immunofluorescence tests, among others. The progression is usually chronic, and therapy varies according to clinical presentation, but generally requires systemic corticosteroid therapy associated with adjuvant immunosuppressive treatment to decrease the adverse effects of corticosteroids. Once the disease is under control, many patients remain stable on low-dose medication, and a significant proportion achieve remission.

Figure 1

Molecular homology between desmoglein 1*, desmoglein 3 and E-cadherin. Desmogleins 1 and 3 are desmosomal transmembrane proteins sharing the same cadherin-like domain structure of E-cadherin. The EC1-EC2 domains of Dsg1 are recognized by pathogenic autoantibodies of FS patients, whereas Dsg3 is bound by autoantibodies from pemphigus vulgaris patients. Autoantibodies against E-cadherin have also been described in mucocutaneous PV, PF, and FS. Legend: Dsg 1 - desmoglein 1; Dsg 3 - desmoglein 3; E-cad - E-cadherin

Figure 2

Desmosome. Legend: Dsg - desmoglein; Dsc - desmocollin; PG - plakoglobin; PP - plakophilin; DP - desmoplakin.

Figure 3

Scheme of the etiopathogenesis of fogo selvagem

Figure 4

Patients with localized forms of FS

Figure 5

Patient with generalized vesiculobullous form evolving to erythroderma

Figure 6

Detachment of acantholytic cells in the granular layer. Note the absence of detachment in the stratum corneum. Histopa thology of FS (Hematoxylin & eosin, x400)

Figure 7

Immu nofluorescence of pemphigus. IgG autoanti bodies directed against the cell surface of kera tinocytes. (x400)

Figure 8

Treatment algorithm for fogo selvage Legend: FS - fogo selvagem; BSA - body surface area; CS - corticoste roid; DDS - diamino-difenyl-sulfone or dapsone; AZA - azathioprine; MMF - mycophenolate mofetil; MTX - methotrexate; IVIg - intravenous immunoglobulin.