Hendri H. Pas

Revertant Mosaicism in Epidermolysis Bullosa Caused by Mitotic Gene Conversion

Mitotic gene conversion acting as reverse mutation has not been previously demonstrated in human. We report here that the revertant mosaicism of a compound heterozygous proband with an autosomal recessive genodermatosis, generalized atrophic benign epidermolysis bullosa, is caused by mitotic gene conversion of one of the two mutated COL17A1 alleles. Specifically, the maternal allele surrounding the mutation site on COL17A1 (1706delA) showed reversion of the mutation and loss of heterozygosity along a tract of at least 381 bp in revertant keratinocytes derived from clinically unaffected skin patches; the paternal mutation (R1226X) remained present in all cell samples. Revertant mosaicism represents a way of natural gene therapy.

Revertant mosaicism in junctional epidermolysis bullosa due to multiple correcting second-site mutations in LAMB3

Revertant mosaicism due to in vivo reversion of an inherited mutation has been described in the genetic skin disease epidermolysis bullosa (EB) for the genes KRT14 and COL17A1. Here we demonstrate the presence of multiple second-site mutations, all correcting the germline mutation LAMB3:c.628G-->A;p.E210K, in 2 unrelated non-Herlitz junctional EB patients with revertant mosaicism. Both probands had a severe reduction in laminin-332 expression in their affected skin. Remarkably, the skin on the lower leg of patient 078-01 (c.628G-->A/c.1903C-->T) became progressively clinically healthy, with normal expression of laminin-332 on previously affected skin. In the other proband, 029-01 (c.628G-->A/c.628G-->A), the revertant patches were located at his arms, shoulder, and chest. DNA analysis showed different second-site mutations in revertant keratinocytes of distinct biopsy specimens (c.565-3T-->C, c.596G-->C;p.G199A, c.619A-->C;p.K207Q, c.628+42G-->A, and c.629-1G-->A), implying that there is not a single preferred mechanism for the correction of a specific mutation. Our data offer prospects for EB treatment in particular cases, since revertant mosaicism seems to occur at a higher frequency than expected. This opens the possibility of applying revertant cell therapy in mosaic EB of the LAMB3 gene by using autologous naturally corrected keratinocytes, thereby bypassing the recombinant gene correction phase.

Bullous pemphigoid successfully controlled by tetracycline and nicotinamide

In 1986, Berk and Lorincz reported the efficacy of tetracycline and nicotinamide in the treatment of bullous pemphigoid (BP). In the present study of seven patients with BP, we found that a regimen of 2 g tetracycline combined with 2 g nicotinamide daily was effective in clearing the skin lesions. Total remission was achieved within 6‐8 weeks, after which the dose was gradually tapered. The mean duration of therapy was 7 months. No effect on the titre of antibasement membrane antibodies was observed. The mode of action of this therapy is unknown.

Bullous Pemphigoid as Pruritus in the Elderly A Common Presentation

IMPORTANCE In the literature, patients with bullous pemphigoid have been reported to have itch without blisters. Clinical observations in these patients have varied from eczematous or urticarial to papular or nodular skin lesions. Here we investigated the spectrum of clinical variants. OBSERVATIONS Fifteen patients with itch without blisters had immunopathologic findings of bullous pemphigoid. Mean age at diagnosis was 81.7 years. No blistering occurred during the mean 2.2 years of follow-up. Mean delay of diagnosis was 2.8 years. Clinical symptoms were heterogeneous: pruritus sine materia (no primary skin lesions), eczematous, urticarial, papular, and/or nodular skin lesions were seen. Treatment with potent topical corticosteroids or methotrexate sodium led to remission in 11 patients. CONCLUSIONS AND RELEVANCE Itch without skin lesions can be the only symptom of bullous pemphigoid. Therefore, it is important to include serologic and direct immunofluorescence in the diagnostic algorithm of itch. We propose the unifying term pruritic nonbullous pemphigoid for all patients with immunopathologic findings of bullous pemphigoid, itch, and no blisters.

Bullous pemphigoid: serum antibody titre and antigen specificity

Abstract 2 antigens have been identified as possible targets for autoantibody depositions in bullous pemphigoid: a 230‐kD protein (BP230) and a 180‐kD protein (BP180). We studied the relationship of these 2 antigens with the immunofluorescence determined serum antibody titre. 2 groups of bullous pemphigoid patients were selected on the basis of immunoblot‐determined antibody specificity. One group (13 patients) had antibody specificity for BP230 and not for BP180, while the other group (9 patients) had antibody specificity for BP180 and not for BP230. The immunofluorescence titres of the circulating antibodies determined on monkey oesophagus substrate displayed, for the BP230‐specific group, a mean of 1:1102. The maximal observed titre was 1:5120. The mean titre in the BP180‐specific group was only 1:29, with a highest titre of only 1:160. This result suggests that in routine indirect immunofluorescence of bullous pemphigoid sera, the contribution of the BP180‐specific antibodies to the total anti‐epidermal basement membrane zone antibody titre is relatively much lower than that of the BP230‐specilic antibodies. Thus, at high dilutions, only the BP230‐speeific antibodies contribute to the overall indirect immunfluorescence titre.

Transition of pemphigus vulgaris into pemphigus foliaceus confirmed by antidesmoglein ELISA profile.

The Correspondence Section serves as a forum for opinion exchange about subjects of general interest such as dermatologic training, relations between dermatologists and pharmaceutical houses, governmental control of dermatology and medical practice in general, peculiarities of dermatology related to geographic, climatic, or racial factors, the flow of information and publications, as well as other concerns the réadership might have. Contributions are welcome and should conform to the usual format for correspondence. Manuscripts will undergo standard editorial procedures. Submit all correspondence to Roberto Cortés Franco. MD , Fax: +52 (5) 665 7691. E-mail: cortesmd@prodigy.net.mx

Enzymatic Breakdown of Type II Collagen in the Human Vitreous

PURPOSE To investigate whether enzymatic collagen breakdown is an active process in the human vitreous. METHODS Human donor eyes were used for immunohistochemistry to detect the possible presence of the matrix metalloproteinase (MMP)-induced type II collagen breakdown product col2-3/4C-short in the vitreous. Western blot and slot blot analyses were used to further identify vitreal type II collagen breakdown products in three age groups with average ages of 25, 45, and 65 years. Purified type II collagen was cleaved by MMPs that are known to occur naturally in the vitreous to elucidate what possible type II collagen breakdown products could thus be formed in the human vitreous. RESULTS By means of both immunohistochemistry and slot blot analysis, col2-3/4C-short was detected in the vitreous. Using Western blot analysis, a range of type II collagen breakdown products was found, mostly in younger eyes, but none of these products contained the neoepitope that characterizes the col2-3/4C-short molecule. Digestion of purified type II collagen by MMPs did not give the same breakdown products as found in the vitreous. CONCLUSIONS The presence of collagen degradation products in the human vitreous supports the hypothesis that enzymatic breakdown is most likely an active process in this extracellular matrix. Based on the size of the degradation products found by Western blot analysis, it is likely that in addition to MMPs, other proteolytic enzymes able to digest type II collagen are also active.

Recombinant Human IgA1 and IgA2 Autoantibodies to Type VII Collagen Induce Subepidermal Blistering Ex Vivo

Subepidermal autoimmune blistering dermatoses (AIBD) are prototypic autoantibody-mediated diseases. In epidermolysis bullosa acquisita (EBA), an autoimmune disease with severe and chronic skin blistering, autoantibodies are directed against type VII collagen. IgG is the predominant autoantibody isotype of EBA, the pathogenicity of which has been demonstrated in a variety of in vivo and ex vivo disease models. In contrast, there is not much evidence for the pathogenicity of IgA, which may appear as the only autoantibody isotype in some EBA patients. To investigate the pathogenic potential of IgA autoantibodies, we generated chimeric V gene–matched human IgA1, IgA2, and control IgG1 autoantibodies directed against type VII collagen. Immobilized immune complexes containing the rIgA1 and rIgA2 autoantibodies induced the dose-dependent release of reactive oxygen species from neutrophil granulocytes, a precondition for blister formation. Moreover, both rIgA1 and rIgA2 induced leukocyte-dependent dermal–epidermal separation in cryosections of human skin. In contrast with rIgG1, neither rIgA1 nor rIgA2 was capable of inducing complement deposition at the dermal–epidermal junction. Because complement activation is a prerequisite for blister induction, this lack of function compared with IgG1 may be compensated for by the stronger activation of neutrophil granulocytes by both IgA1 and IgA2. For IgG-mediated AIBD, immunoadsorption therapy is a convenient treatment modality for the removal of pathogenic autoantibodies, particularly in treatment-resistant cases. The results of this study show the pathogenic potential of IgA autoantibodies and support the development of adsorber matrices for IgA-mediated AIBD.

Truncated type XVII collagen expression in a patient with non-Herlitz junctional epidermolysis bullosa caused by a homozygous splice-site mutation

Type XVII collagen (180-kDa bullous pemphigoid antigen) is a structural component of hemidesmosomes. Mutations in the type XVII collagen gene (COL17A1) have been established to be the molecular basis of non-Herlitz junctional epidermolysis bullosa (JEB-nH), an inherited skin blistering disorder. Here we report for the first time truncated type XVII collagen expression, caused by homozygosity for a COL17A1 donor splice-site mutation (4261+1 g → c), which was identified by PCR amplification on genomic DNA. By RT-PCR and sequencing of cDNA derived from mRNA from the patient’s cultured keratinocytes, we provide evidence of cryptic splicing and exon skipping, most abundantly of exon 52. JEB-nH patients with COL17A1 splice-site mutations resulting in an exon skip often have no immunologically detectable type XVII collagen. However, in our patient with the generalized atrophic benign epidermolysis bullosa subtype, a small amount of type XVII collagen was detectable in the skin, and immunoblotting of cultured keratinocytes revealed that the 180-kDa protein was 10 kDa shorter. We hypothesize that the function of this truncated type XVII collagen polypeptide, which is expressed at low levels, is impaired, explaining the JEB-nH phenotype.

Staphylococcal scalded skin syndrome: loss of desmoglein 1 in patient skin

Staphylococcal scalded skin syndrome (SSSS) is a blistering disease of the skin caused by an infection with certain strains of Staphylococcus aureus. In vitro studies have suggested that exfoliative toxins secreted by these bacteria cleave the desmosomal adhesion molecule desmoglein 1 leading to loss of cell-cell contact in the superficial epidermis. In this study we investigated the fate of desmoglein 1 in biopsies of patients with SSSS to see whether the ectodomain of desmoglein 1 is cleaved. Our data largely confirm previous in vitro data. The different biopsies demonstrated the loss of the ectodomain of desmoglein 1 to different degrees. The endodomain of desmoglein 1 meanwhile remained present. Most remarkably, in one of our patients, the immunofluorescent analysis demonstrated that not desmoglein1 but desmocollin 1, another desmosomal cadherin, became affected. This raises the question if other toxins and/or other bacteria than Staphylococcus aureus might also induce SSSS.