Detection of driver mutations in BRAF can aid in diagnosis and early treatment of dedifferentiated metastatic melanoma.

Dedifferentiated metastatic melanoma can pose a significant diagnostic challenge, especially if the history of primary melanoma is not known or is remote. BRAF and NRAS mutations are common melanoma driver mutations that are usually sequenced to evaluate for treatment targets. We evaluated whether BRAF and NRAS mutational testing could contribute to the diagnosis of dedifferentiated metastatic melanoma when immunostains are negative. Seven patients with melanoma who had an additional diagnosis of poorly differentiated sarcoma with negative melanocytic immunostains were tested for BRAF and NRAS mutations. Three patients showed identical BRAF mutations in the melanoma and the poorly differentiated sarcoma and hence were re-classified as metastatic dedifferentiated melanoma. In these three patients, there was an average delay of 7 months before appropriate testing, workup and treatment for metastatic melanoma was initiated. Two of these patients currently have stable metastatic disease and show sustained therapeutic response to melanoma-specific treatment including BRAF inhibitors. BRAF mutational analysis should therefore be considered in cases of poorly differentiated sarcoma, especially if there is a known history of melanoma or with unusual localization of disease. The administration of melanoma-specific treatments in such dedifferentiated cases can show therapeutic response, highlighting the importance of rendering accurate diagnoses on such cases.

Fluorescence in situ hybridization (FISH) as an aid for the diagnosis of graft-versus-host disease in two multivisceral organ transplant patients.

We herein describe 2 cases of adult multivisceral transplant patients who developed graft-versus-host disease manifesting predominantly as lichenoid skin papules and plaques. The diagnosis was supported by histopathology but ultimately corroborated by the utilization of the fluorescence in situ hybridization (FISH) technique using X and Y chromosome probes on unstained biopsy slides. In both cases, FISH revealed a high percentage of donor-derived cells as part of the inflammatory infiltrate in the skin biopsy. This report adds to the previous publications showing the utility of FISH in corroborating the diagnosis of graft-versus-host disease in transplant patients with unmatched sex donor.

Progression of toxic epidermal necrolysis after tanning bed exposure.

BACKGROUND: In addition to recreational tanning bed use, UV radiation exposures are sometimes sought to self-treat skin conditions. The ability of tanning bed radiation exposure to trigger toxic epidermal necrolysis has not been reported. OBSERVATIONS: A young woman attempted to treat a self-limiting drug hypersensitivity reaction via tanning bed radiation exposure, which resulted in a systemic toxic epidermal necrolysis-like reaction. Studies with cultured keratinocytes and an epithelial cell line reveal that UV-A radiation can synergize with other stimuli such as phorbol esters or interleukin 1 to produce large amounts of tumor necrosis factor, providing a potential mechanism for this exaggerated reaction. CONCLUSION: In addition to inducing photodamage and skin cancer, tanning bed radiation exposure can trigger a toxic epidermal necrolysis-like reaction, possibly via the exaggerated production of keratinocyte cytokines such as tumor necrosis factor.

Environmental risk factors in endemic pemphigus foliaceus (fogo selvagem).

An ongoing sero-epidemiological study of the Terena reservation of Limao Verde, known to have a high prevalence and incidence of FS, has revealed important information about this autoimmune disease. During surveillance of this population of approximately 1,200, which began in 1994, we documented 43 FS cases and studied the transition from the normal state to the disease state in several of these individuals. Furthermore, we established that FS patients as well as a large number of normal individuals on the reservation possess anti-dsg1 autoantibodies. The following interesting observations were made: (1) the ectodomain of dsg1 contains epitopes recognized by both autoantibodies and T cells from FS patients; (2) pathogenic anti-dsg1 autoantibodies in FS belong to the IgG4 subclass; (3) nonpathogenic anti-dsg1 autoantibodies of the IgG1 subclass were detected in normal individuals from Limao Verde and in patients in the preclinical stage of the disease; (4) anti-dsg1 autoantibodies from normal individuals and patients in the preclinical stage of FS recognize the EC5 domain of dsg1, whereas pathogenic anti-dsg1 autoantibodies bind the EC1/EC2 domains; (5) houses of FS patients are rustic, with thatched roofs and walls and dirt floors; (6) there was a high frequency of hematophagous insects (bedbugs and kissing bugs) in the houses of FS patients; (7) previous studies revealed that the predominant black fly on this reservation belongs to the species Simunlium nigrimanum. These findings suggest that the environmental antigen(s) triggering the autoimmune response in FS may be linked to exposure to hematophagous insects.

Characterization of a subgroup of patients with dermatitis herpetiformis with nonclassical histologic features.

Dermatitis herpetiformis (DH) is an autoimmune disease mediated by IgA antibodies. The diagnosis of DH is based on clinical presentation, biopsy for hematoxylin and eosin, and direct immunofluorescence. The chief hematoxylin and eosin finding is a subepithelial blister with neutrophils in dermal papillae. The direct immunofluorescence findings are deposition of IgA and sometimes C3 at the basement membrane with accentuation in dermal papillae. Immunofluorescence is thought to be a sensitive and specific assay in DH, and there are no other known diseases with this pattern of immunofluorescence. The aim of this project was to determine the prevalence of nonclassical histologic findings in DH. We studied 24 cases of DH received at our institution. All cases had clinical findings of DH as well as positive direct immunofluorescence with IgA. We found that 9 of 24 cases (37.5%) had nonspecific H&E findings of a lymphocytic infiltrate only with fibrosis in the dermal papillae and ectatic capillaries. The remaining 15 cases had classic findings of multilocular neutrophilic microabscesses in the dermal papillae. These findings were reproduced on step sectioning. These findings suggest that routine histology may be quite nonspecific in DH and direct immunofluorescence or other more specific immunologic assay is an essential adjunct to diagnosis.

A subset of pemphigus foliaceus patients exhibits pathogenic autoantibodies against both desmoglein-1 and desmoglein-3.

In pemphigus vulgaris the major pathogenic antibody binds desmoglein-3, and mediates mucosal disease. Development of cutaneous disease is associated with acquisition of antibodies to desmoglein-1. In pemphigus foliaceus, and its endemic form, fogo selvagem by contrast, the major pathogenic antibody recognizes desmoglein-1 and mediates cutaneous disease only. In this study, we sought to determine the prevalence of antibodies to desmoglein-3 in patients with pemphigus foliaceus and fogo selvagem. We produced recombinant desmoglein-1 and desmoglein-3, and used them in highly sensitive and specific enzyme-linked immunosorbent assays, as well as immunoprecipitation assays. We detected antibodies to desmoglein-3 in 19 of 276 patients with pemphigus foliaceus and fogo selvagem, who had cutaneous disease only. We showed that these antibodies to desmoglein-3 could be absorbed in a concentration-dependent manner by desmoglein-3 but not by desmoglein-1. Also antibodies to desmoglein-1 could be absorbed in a concentration-dependent manner by desmoglein-1 but not desmoglein-3. This suggests that two separate species of antibody are present rather than one antibody capable of cross-reacting with both desmoglein-1 and desmoglein-3. Finally, it was shown that affinity-purified antibodies to desmoglein-3 from patients with pemphigus foliaceus and fogo selvagem induced a pemphigus vulgaris-like skin disease in mice by passive transfer. These results suggest that a subset of patients with pemphigus foliaceus and fogo selvagem have antibodies to desmoglein-3 that may be involved in the pathogenesis of their cutaneous disease.