Clinical heterogeneity in epidermolysis bullosa: speculations on causation and consequence for research

Kalinin is abnormally expressed in epithelial basement membranes of Herlitz's junctional epidermolysis bullosa patients

Kalinin is an extracellular adhesion molecule specific to epithelial basement membranes (BM) identified as a component of anchoring filaments of hemidesmosomes. This heterotrimeric protein is synthesized by cultured normal human keratinocytes and is involved in cell attachment. In indirect immunofluorescence studies, the epidermal BM of patients with junctional epidermolysis bullosa (JEB) of Herlitz's type were found not to be reactive with the anti-kalinin monoclonal antibodies ka146 and K140 and displayed a decreased immunoreactivity to two anti-kalinin antibodies cross-reacting with K-laminin, an anchoring filament component recently described. The intrinsic defect of JEB keratinocytes in the synthesis of kalinin was further documented by indirect immunofluorescence on in vitro cultures of these cells. In non-Herlitz JEB patients, staining of BM was constantly detected. Impairment of expression of kalinin correlated with the lack of reactivity to the monoclonal antibody GB3, which detects the BM component nicein/BM600. These results clearly demonstrate a defect of kalinin expression in epithelial basement membranes of Herlitz JEB patients and suggest that kalinin may play a role in the pathogenesis of the disease. Further studies are in progress to define possible relationships between kalinin and nicein.

Genetic linkage of recessive dystrophic epidermolysis bullosa to the type VII collagen gene

Generalized mutilating recessive dystrophic epidermolysis bullosa (RDEB) is characterized by extreme skin fragility owing to loss of dermal-epidermal adherence. Immunohistochemical studies have implicated type VII collagen, the major component of anchoring fibrils, in the etiology of RDEB. In this study, we demonstrate genetic linkage of the type VII collagen gene and the generalized mutilating RDEB phenotype. We first identified a Pvull polymorphic site by digestion of an amplified product of the type VII collagen gene, which was shown to reside within the coding region. Genetic linkage analysis between this marker and the RDEB phenotype in 19 affected families which were informative for this polymorphism showed no recombination events, and gave a maximum lod score of 3.97 at a recombination fraction (theta) of 0, demonstrating that this DNA region is involved in this form of RDEB. These data provide strong evidence that the type VII collagen gene, which has also been linked with the dominant form of the disease, harbors the mutation(s) causing the generalized mutilating form of RDEB in these families, thus underscoring the major functional importance of type VII collagen in basement membrane zone stability.

Junctional epidermolysis bullosa: a mild variant in two Indian sisters

Two sisters developed a bullous skin disease in early childhood. The disease had features of junctional epidermolysis bullosa but differed clinically from previously recorded variants.

Exclusion of linkage between the collagenase gene and generalized recessive dystrophic epidermolysis bullosa phenotype

Generalized recessive dystrophic epidermolysis bullosa (RDEB) is a severe inherited autosomal disease characterized by dermolytic blister formation. Enhanced collagenase and/or abnormal collagenase have been reported in skin from affected patients, suggesting that collagenase could be responsible for the absence of anchoring fibrils in this disorder. We used a genetic linkage approach to test the hypothesis that this disease is due to a defect in the collagenase gene in nine affected families. Analysis of amplified genomic DNA fragments of the collagenase gene by means of denaturing gradient gel electrophoresis (DGGE) allowed us to detect intragenic polymorphisms, which were subsequently characterized by direct genomic sequencing. Segregation analysis of these polymorphic sites showed exclusion of linkage between the collagenase gene and generalized RDEB phenotype in a family with consanguineous parents and three affected children. However, the possibility of linkage with the collagenase gene in the other eight families tested could not be excluded. The genetic markers described here provide a tool for investigating genetic linkage in other affected families. Overall, our results show that generalized RDEB can be caused by a defect in a gene other than the collagenase gene, and support the hypothesis that the genetic defect lies in abnormal anchoring fibril formation.

Oral soft tissues in hereditary epidermolysis bullosa

Epidermolysis bullosa (EB) is associated with diverse oral manifestations, which can potentially involve both hard and soft tissues, depending on the specific EB subtype. This study determined the frequency and extent of oral soft tissue involvement in the inherited forms of EB. Examination of 216 affected persons revealed significant differences in the oral soft tissue involvement among the various types of EB. The frequency of oral involvement was greater in the dominant dystrophic (81.1%) and simplex (generalized, 58.6%; localized, 34.7%) types than previously reported. The marked frequency of oral blistering was similar in both major subtypes of junctional (Herlitz, 83.3%; non-Herlitz, 91.6%) and recessive dystrophic EB (generalized, 100%; localized, 92.3%). Obliteration of the oral vestibule, ankyloglossia, and microstomia were consistent findings in generalized recessive dystrophic EB. Oral milia were present in all major EB categories, most prevalently in the dystrophic forms, but were not seen in all the distinct EB subtypes. These findings indicate that although there are no pathognomonic intraoral soft tissue manifestations in the various forms of inherited EB, there are predictable patterns of involvement associated with specific subtypes of this disease. Understanding the oral involvement associated with EB may aid clinicians in the development of more advanced therapeutic approaches that are compatible with and directed at the unique characteristics of each EB subtype.

Extracellular matrix of the skin: 50 years of progress

The extracellular connective tissue matrix of the skin is a complex aggregate of distinct collagenous and non-collagenous components. Optimal quantities and delicate interactions of these components are necessary to maintain normal physiologic properties of skin. This overview summarizes the progress made in understanding the normal biology and biochemistry of the extracellular matrix, and will highlight cutaneous diseases with underlying molecular defects in the structure and expression of extracellular matrix components.

Hemidesmosomes and anchoring fibril collagen appear synchronously during development and wound healing

Bullous pemphigoid antisera and monoclonal antibodies to type VII collagen were used to localize hemidesmosomes and anchoring fibrils, respectively, in tissues of developing eyes and healing corneal wounds of New Zealand white rabbits. In the 17-day fetal rabbit eye, both antibodies colocalize to the epithelial-stromal junction of the lid and conjunctival region, but neither binds to the cornea, and electron microscopy demonstrates hemidesmosomes only where the antibodies bind. By 20 days of fetal development, the antibodies colocalize in cornea, and, by electron microscopy, hemidesmosomes are shown to be present as well. In healing 7-mm corneal wounds, both antibodies colocalize at the wound periphery within 66 h. By electron microscopy, hemidesmosomes along small segments of basal lamina are also shown to be present at the wound periphery at this time. These demonstrations of the synchronous assembly of hemidesmosomes and anchoring fibrils support the hypothesis of linkage of hemidesmosomes through the basement membrane to anchoring fibrils.

Treatment of junctional epidermolysis bullosa with epidermal autografts

We have successfully treated chronic facial erosions in three boys with junctional epidermolysis bullosa. In each patient, keratinocytes were harvested from the roof of suction blisters created on clinically uninvolved skin. They were grown in tissue culture on collagen sponges and grafted onto facial erosions that were previously treated with 2% mupirocin ointment. This experimental antibiotic ointment has proved efficacy in eradicating cutaneous pathogens such as Staphylococcus aureus from chronic wounds. In two patients, complete reepithelialization was achieved over 7 and 10 months, respectively, and partial reepithelialization occurred in another patient in whom treatment is ongoing. Epidermal autografts are a promising means for improving function and appearance in eroded skin caused by junctional epidermolysis bullosa.

Identification of an epidermal basement membrane defect in recessive forms of dystrophic epidermolysis bullosa by LH 7:2 monoclonal antibody: use in diagnosis

LH 7:2 is a monoclonal antibody that was raised against an extract of human epidermal cells and identifies an epitope within the lamina densa of the basement membrane of stratified squamous epithelia. Using indirect immunofluorescence we found intense labelling with LH 7:2 at the epidermal basement membrane (EBM) of normal skin, and in skin samples from patients with simplex, junctional, dominantly inherited dystrophic and acquired forms of epidermolysis bullosa (EB), as well as bullous pemphigoid. Staining was absent or only very faint in generalized recessive dystrophic EB (RDEB), and patchily reduced in the localized form of RDEB. We conclude that LH 7:2 recognizes an EBM antigen which may be important in the pathogenesis of RDEB. Moreover, the antibody provides a useful probe for the rapid diagnosis of RDEB and is of special value in helping to discriminate between localized RDEB and typical dominant dystrophic EB--conditions which closely resemble each other clinically and which cannot be distinguished by means of transmission electron microscopy.