Fogo Selvagem Workup

Updated: Apr 16, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: William D James, MD  more...
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Workup

Laboratory Studies

Indirect IF testing of the patient's serum: Intercellular fluorescence in the epidermis (anti-IgG autoantibodies) is observed. Often, a positive relationship between the intercellular fluorescence and the activity of the disease exists. [33] Direct IF of a biopsy sample of perilesional skin: Intercellular fluorescence in the epidermis (anti-IgG or anti-C3 autoantibodies) is observed.

The Colombian variant of endemic pemphigus foliaceus was found to have complement/C5-b9 in lesional skin correlating with disease severity. [34]

With immunoblotting, epidermal extracts have reactivity against desmoglein 1 substrate (160 kd in 33% of the cases).

With immunoprecipitation, bovine desmoglein 1 substrate has (45- or 80-kd fragment) 100% reactivity with fogo selvagem sera. Recombinant desmoglein 1 substrate (rDsg1-His) has 100% reactivity with fogo selvagem sera. Note the image below.

Immunoprecipitation with the recombinant desmoglei Immunoprecipitation with the recombinant desmoglein 1. Lane 1 is the result in normal human serum. Lanes 2-7 are findings in sera from patients with fogo selvagem. Lanes 2-7 show the reaction of the sera against the extracellular domain of desmoglein 1.

The immunoglobulin M antidesmoglein-1 response appears to distinguish Brazilian pemphigus foliaceus (fogo selvagem) from other forms of pemphigus. However, immunoglobulin M antidesmoglein-1, which is common in fogo selvagem patients in their native environment and uncommon in other pemphigus phenotypes, is also infrequent in fogo selvagem patients who migrate to urban areas. [35]

With enzyme-linked immunosorbent assay (ELISA), rDsg1-His has 96% positivity with fogo selvagem sera. The sensitivity of indirect IF and ELISA in detecting intercellular antibodies in fogo selvagem was studied. [36] ELISA (rDsg1) was found to be slightly more sensitive than indirect IF in detecting circulating autoantibodies. However, no test is 100% accurate in differentiating fogo selvagem from pemphigus vulgaris. In this study, 4 (12%) of 32 patients with fogo selvagem (cutaneous diseases only) also had desmoglein-3 antibodies.

The development of an IgG4-based predictor of fogo selvagem may be possible. [37] Identifying individuals at increased risk or those with preclinical fogo selvagem may facilitate disease prevention, and it may assist in identifying the etiological agent or triggering factors.

Tzanck smears may reveal acantholytic cells.

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Histologic Findings

Pemphigus foliaceus begins with acantholysis of the upper epidermis, which often results in a subcorneal cleft. The subcorneal cleft usually enlarges and detaches without bullae formation, although a bulla may form, with acantholysis at both the roof and the floor.

More established lesions may have acanthosis and mild-to-moderate papillomatosis. Hyperkeratosis and parakeratosis may also be evident, with dyskeratotic cells within the granular layer. A mild dermal lymphocytic infiltrate, often associated with the presence of eosinophils, is observed.

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