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Background Trichoadenoma is a rare benign follicular tumor first described by Nikolowski 50 years ago. Both trichoadenoma and desmoplastic trichoepithelioma are composed of cords of epithelial cells and cornifying cysts embedded in sclerotic stroma. In trichoadenoma the cystic component predominates, while desmoplastic trichoepithelioma is a mostly solid neoplasm. Therefore trichoadenoma was suggested to represent a cystic variant of desmoplastic trichoepithelioma. Objective The aim of this study was to investigate whether the morphologic overlap between trichoadenoma and desmoplastic trichoepithelioma translates into a similar immunohistochemical profile. Methods We studied 19 trichoadenomas and 21 desmoplastic trichoepitheliomas for cytokeratin 20, Ber-EP4, and androgen receptor expression. Results Eighteen of 19 trichoadenomas and all desmoplastic trichoepitheliomas demonstrated the presence of Merkel cells as detected by a monoclonal antibody against cytokeratin 20. In contrast, while all desmoplastic trichepitheliomas were positive for Ber-EP4, only 4 of 19 trichoadenomas showed any kind of reactivity for this marker. None of the trichoadenomas or desmoplastic trichoepitheliomas expressed androgen receptor. Limitations This study is limited by the moderate number of these rare tumors available for immunohistochemical analysis. Conclusion Our data demonstrate that trichoadenoma typically retains cytokeratin 20–positive Merkel cells but lacks Ber-EP4 and androgen receptor expression. Trichoadenoma is a distinct follicular tumor related but not identical to desmoplastic trichoepithelioma.

We report an unusual case of congenital melanocytic nevus presenting in a 19-year-old African woman as widespread papules and variably sized nodules and tumors affecting the entire body, including the palms, soles, and oral mucous membrane. Histopathologic examination of 3 representative skin lesions showed mainly dermal aggregations of round to oval, focally pigmented, monomorphous melanocytes, arranged in nodular and plexiform patterns. Scattered areas with spindle-shaped dendritic melanocytes surrounded by fibrosis were also noted in the center of the lesions. The clinical and histopathologic findings were similar to those in 2 other previously reported cases, except that in 1 of the earlier cases the skin nodules were composed of spindle-shaped cells, suggesting a type of blue nevus. The findings in our case indicate a broader spectrum of morphologic features in this condition, with dermal aggregations of melanocytes showing congenital features, representing a common histopathologic denominator. Based on this observation, we suggest the term "widespread congenital dermal nevus with large nodules" to be the most appropriate for this rare, but distinctive, type of congenital nevus.

Pemphigoid gestationis (PG) is an autoimmune pregnancy-associated subepidermal blistering disease. It usually affects skin and, rarely, mucous membranes. In the vast majority of patients with PG, the autoimmune response is directed to the membrane-proximal NC16A domain of the 180-kd bullous pemphigoid (BP) antigen (BP180) and is mediated by IgG1 and IgG3 autoantibodies. We report the case of a patient with PG associated with extensive lesions on oral mucous membranes. Immunoblotting studies demonstrated the presence of circulating IgA autoantibodies in the patient's serum that were exclusively directed to a 49 amino acid stretch on the C-terminal portion of the BP180 ectodomain located 800 amino acids downstream from NC16A. This C-terminal stretch of BP180 has previously been demonstrated to localize to the lamina lucida/lamina densa interface and to be recognized by IgG and IgA antibodies in a subgroup of patients with cicatricial pemphigoid as well as by IgG autoantibodies in some BP sera. Our patient's lesions healed without scarring within 6 weeks after delivery of a healthy child. The findings in this patient extend the clinical and immunopathologic spectrum of PG. (J Am Acad Dermatol 2002;47:780-4.)

Background: Dermatitis herpetiformis (DH) is highly associated with celiac disease. Recently, tissue transglutaminase (tTG) was identified as the autoantigen of IgA antibodies in celiac disease. The prevalence of antibodies to tTG in DH patients is not known. Objective: The purpose of this study was to determine whether DH patients show circulating IgA autoantibodies to tTG, to compare their serum levels with those from patients with other subepidermal autoimmune bullous diseases, and to correlate levels of antibodies to tTG with the extent of small bowel disease. Methods: Sera were obtained from consecutive patients with DH (n = 11), linear IgA disease (n = 15), bullous pemphigoid (n = 10), and epidermolysis bullosa acquisita (n = 6) and were studied by indirect immunofluorescence on monkey esophagus and NaCl-split human skin. IgA reactivity to tTG was measured by enzyme-linked immunosorbent assay. The extent of mucosal involvement in jejunal biopsy specimens was assessed according to the grading of Marsh. Results: All untreated DH patients showed circulating IgA autoantibodies to tTG. One DH patient already undergoing therapy, the 15 patients with linear IgA disease, and all other controls revealed no autoantibodies to tTG. In addition, serum levels of IgA anti-tTG antibodies reflected the degree of histopathologic changes in jejunal mucosa from biopsy specimens in DH patients. Conclusion: Our results show that circulating IgA autoantibodies to tTG are detectable in DH but not in linear IgA disease or other subepidermal autoimmune bullous diseases. The levels of IgA anti-tTG antibodies reflect the extent of histopathologic changes of the jejunal mucosa in DH. (J Am Acad Dermatol 1999;41:957-61.)

Background Skin biopsies are commonly performed to confirm drug-induced exanthem (DIE). However, the relevance of histologic examination in discriminating between DIE and non-DIE (NDIE) is controversial. Objective A retrospective analysis was performed to evaluate the reliability of histologic diagnosis of DIE. Methods In all, 91 patients with a skin biopsy specimen of an acute exanthem temporally related to a single identifiable drug underwent complete allergy testing. Their biopsy specimens were retrospectively re-evaluated by 2 dermatopathologists blinded to the original reports to test for discrimination between DIE versus NDIE. Results In 35 patients, non-IgE-mediated drug allergy was confirmed by allergy testing, whereas in 56 patients drug hypersensitivity could be excluded. Sensitivity of pathology reports for diagnosis of DIE reached 62.9% with a positive predictive value of 40.7%. Specificity was 41.1% with a negative predictive value of 69.7%. No significant difference in tissue eosinophilia was detected between DIE and NDIE. Limitations This was a retrospective study. Conclusions Dermatopathologic evaluation of skin biopsy specimens is of limited use in differentiating between DIE and NDIE. All efforts should be made to subject these patients to thorough allergy testing for definitely confirming or ruling out drug hypersensitivity.

Background Dermatitis herpetiformis (DH) is a cutaneous manifestation of celiac disease (CD), the latter being identified by circulating autoantibodies against native gliadin (nGli), tissue transglutaminase (tTG), endomysium, or a combination of these. Recently, a novel serologic assay using deamidated gliadin-analogous fusion peptides (GAF3X) showed high diagnostic sensitivity in patients with CD. Objective The aim of this study was to explore the anti-GAF3X enzyme-linked immunosorbent assay (ELISA) and to compare it with a panel of classic CD-related serologic tests in patients with DH. Methods Antibodies against nGli, GAF3X, and tTG were determined by separate ELISA tests and against endomysium by indirect immunofluorescence microscopy in 45 patients with DH and 52 control patients (30 patients with bullous pemphigoid and 22 patients with linear IgA disease). A total of 24 patients with DH underwent intestinal biopsies to confirm underlying CD. Results Antibodies to nGli were detected in 26 (58%) (IgA) and 24 (53%) (IgG), to GAF3X in 38 (84%) (IgA) and 36 (80%) (IgG), to tTG in 35 (78%) (IgA), and to endomysium in 32 (71%) (IgA) patients with DH. Combined testing of IgA and IgG antibodies to GAF3X detected 7 of 10 (70%) IgA-anti-tTG-negative patients with DH and together with the IgA-anti-tTG ELISA showed the highest serologic hit rate (93%) for CD. Limitations Intestinal biopsies were not performed in all patients with DH. Conclusion The novel anti-GAF3X ELISA shows a higher sensitivity to detect CD-associated autoantibodies in patients with DH compared with tests using nGli, tTG, or endomysium as substrates.

Background Rituximab has been increasingly used in autoimmune blistering dermatoses, mainly in pemphigus. However, only a few larger case series are available on this subject and information on the efficacy of retreatment with rituximab during relapses is lacking. Objective We sought to determine efficacy and adverse effects of adjuvant rituximab. Methods Seventeen patients with refractory autoimmune blistering dermatoses (pemphigus vulgaris [PV], n = 8; pemphigus foliaceus [PF], n = 2; bullous pemphigoid [BP], n = 2; mucous membrane pemphigoid, n = 5) were treated 4 times with rituximab at an individual dose of 375 mg/m 2 in weekly intervals or twice with 1000 mg 2 weeks apart. Six of 8 patients with a relapse after this regimen received rituximab again twice with 1000 mg in a 2-week interval. Results All lesions cleared in 14 patients (7 PV, two PF, two BP, 3 mucous membrane pemphigoid), whereas partial healing was found in 3 others (one PV, two mucous membrane pemphigoid). Relapses occurred in 8 patients (5 PV, two PF, one BP). Retreatment with rituximab again resulted in complete (two PV, one PF, one BP) or partial (two PV) remission. Serious side effects associated with rituximab were not observed. Limitations Rituximab has been combined with various other immunosuppressive or immunomodulatory treatments. Conclusion Adjuvant rituximab is effective and well tolerated not only in patients with pemphigus but also with pemphigoid. Efficacy and safety of rituximab are maintained when it is readministered during relapses.

Pemphigus and the pemphigoid group of diseases are distinct autoimmune conditions in which autoantibodies with different specificities cause skin blistering by different mechanisms. Transitions and associations between these two groups of autoimmune diseases are rare. Here, we report a patient with long-standing pemphigus foliaceus, in whom clinical remission was eventually induced. Shortly thereafter, he developed the clinical, histologic, and immunopathological changes of bullous pemphigoid. This case offered the rare opportunity to serologically monitor serum levels of both anti-BP180 and BP230 during the preclinical stage of bullous pemphigoid. Of interest, although the autoimmune response clearly shifted with regard to the target antigens, the patient's autoantibodies against desmosomal and hemidesmosomal components showed the same IgG subclass distribution.

Background Dermatitis herpetiformis (DH) is a cutaneous manifestation of gluten-sensitive enteropathy (celiac disease). Patients with DH demonstrate circulating IgA antibodies against epidermal transglutaminase (eTG) and tissue transglutaminase (tTG). It has been suggested that eTG is the autoantigen of DH. Objective The purpose of this study was to characterize the autoimmune response to eTG and tTG in patients with DH on a normal or gluten-free diet (GFD). Methods Sera from 52 patients with DH were studied for the presence of IgA antibodies to eTG and tTG by enzyme-linked immunosorbant assay. In 38 patients, serum was obtained before initiation of a GFD, whereas 14 patients had been on a GFD for at least 2 years. Results Autoantibodies against eTG were detected in 36 of 38 patients (95%) and those against tTG in 30 of 38 patients (79%) with DH on a normal diet. Of 14 patients on a long-term GFD, 7 patients were free of DH lesions and did not require dapsone treatment. None of these patients showed circulating antibodies against eTG or tTG. The remaining 7 patients on a GFD were not able to stop taking dapsone. All these patients demonstrated anti-eTG antibodies, whereas only 3 of them showed additional reactivity against tTG. Limitation Autoantibody levels against eTG and tTG before and after introduction of a GFD were not examined in the same patients. Conclusion Our data suggest that antibodies to eTG are the most sensitive serologic marker in treated and untreated patients with DH and confirm the central role of eTG in the pathogenesis of this disease. (J Am Acad Dermatol 2009;61:39-43.)

Background Anti-laminin 5 mucous membrane pemphigoid (MMP) is an autoimmune blistering disease characterized by autoantibodies against the major basement membrane component laminin 5 (laminin 332, epiligrin). Objective and Methods We reviewed 17 biopsy specimens from 9 patients with anti-laminin 5 MMP in an attempt to define typical histopathologic features of the disease. Results Fifteen specimens showed subepidermal blister formation, while two biopsy specimens revealed an epithelial ulcer. In 11 biopsies a sparse to moderate inflammatory infiltrate composed of lymphocytes and neutrophils with some eosinophils was observed. Four biopsies showed a dense infiltrate dominated by neutrophils in two cases and by eosinophils in one case. The remaining biopsy revealed a dense lymphoplasmacellular infiltrate without granulocytes. Scarring of the upper dermis was present only in 5 specimens. Immunohistochemical analysis localized type IV collagen to the dermal side of the blister, suggesting that split formation occurred within the lamina lucida of the cutaneous basement membrane. Limitations The number of patients studied was relatively small. Conclusions Histopathology of anti-laminin 5 MMP is characterized by subepidermal blistering and a sparse to moderate superficial lymphohistiocytic infiltrate with neutrophils and/or eosinophils. Both infiltrate density and composition may vary, making anti-laminin 5 MMP indistinguishable from other autoimmune subepidermal blistering diseases by histopathology alone. Scarring is present only in a minority of cases and is not a sensitive clue to the diagnosis of anti-laminin 5 MMP.

We describe a patient who developed an exclusively perianal-intergluteal vesicular eruption after receiving a course of ampicillin/sulbactam. Direct immunofluorescence microscopy of perilesional skin demonstrated linear deposits of IgA along the dermal-epidermal junction. Circulating IgA autoantibodies against the 120-kd soluble ectodomain of bullous pemphigoid antigen 180 (LAD-1 autoantigen) were detected by immunoblotting. Discontinuation of the antibiotics resulted in a rapid resolution of the skin lesions. This is a most unusual case of localized drug-induced linear IgA disease.