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Kindler syndrome is a rare, autosomal recessive genodermatosis, caused by mutations in the FERMT1 gene. It is thought to be primarily a skin disease, but other organs may also be involved. We report a case of a novel mutation of FERMT1 gene in a patient with a probable new phenotype of Kindler syndrome, including colitis and primary sclerosing cholangitis. A 42-year-old man, born to first cousin parents, was referred to our outpatient dermatology clinic with an unknown dermatosis since birth. He presented with neonatal blistering and developed photosensitivity and changes in skin pigmentation during childhood. Since the age of 20, he has had regular follow-up in the gastroenterology clinic, owing to esophageal stenosis, ulcerative colitis, and primary sclerosing cholangitis. Clinical examination revealed jaundice, poikiloderma, diffuse cigarette paper-like atrophy on dorsal surfaces of the hands, and palmoplantar hyperkeratosis. Skin biopsy showed epidermal atrophy covered by orthokeratotic hyperkeratosis. DNA molecular analysis revealed FERMT1 homozygous mutation c.1179G>A, p.W393X, which has not been reported before. The intestinal phenotype of Kindler syndrome has already been defined previously. However, to the best of our knowledge, no other case of primary sclerosing cholangitis in a patient with Kindler syndrome has been reported.

Development of an intact epidermis is critical for maintaining the integrity of the skin. Patients with epidermolysis bullosa (EB) experience multiple erosions, which breach the epidermal barrier and lead to increased microbial colocalization of wounds, infections and sepsis. The cytoskeletal protein Flightless I (Flii) is a known regulator of both development and wound healing. Using Flii(+/-), WT and Flii(Tg/Tg) mice, we investigated the effect of altering Flii levels in embryos and adult mice on the development of the epidermal barrier and, consequently, how this affects the integrity of the skin in EB. Flii over-expression resulted in delayed formation of the epidermal barrier in embryos and decreased expression of tight junction (TJ) proteins Claudin-1 and ZO-2. Increased intercellular space and transepidermal water loss was observed in Flii(Tg)(/Tg) adult mouse skin, while Flii(Tg/Tg) keratinocytes showed altered TJ protein localization and reduced transepithelial resistance. Flii is increased in the blistered skin of patients with EB, and over-expression of Flii in experimental EBA showed impaired Claudin-1 and -4 TJ protein expression and delayed recovery of functional barrier post-blistering. Immunoprecipitation confirmed Flii associated with TJ proteins and in vivo actin assays showed that the effect of Flii on actin polymerization underpinned the impaired barrier function observed in Flii(Tg/Tg) mice. These results therefore demonstrate an important role for Flii in the development and regulation of the epidermal barrier, which may contribute to the impaired healing and skin fragility of EB patients., (Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

Inherited keratinizing disorders are caused by mutations in the genes encoding cornified cell envelope proteins, enzymes and their inhibitors, adhesion molecules, cytoskeletal proteins and others in the epidermis. These molecules are known to regulate differentiation, proliferation and cell adhesions. Intriguingly, some keratinizing disorders show blistering skin lesions, while some inherited blistering disorders show abnormal keratinization. Therefore, hereditary keratinizing and blistering diseases are closely related and show overlapping genetic backgrounds. In this review, we overviewed keratinizing and blistering disorders in terms of overlapping of the two disease groups. Gene mutations in desmosomal components cause striate keratoderma, Naxos disease, epidermolytic palmoplantar keratoderma and plakophilin deficiency, which first show skin fragility and blisters and later hyperkeratosis. Gene mutations in hemidesmosomal components cause various forms of epidermolysis bullosa, some of which show hyperkeratosis on the nails, palms and soles, in addition to blister formation. Diseases with gene mutations in calcium pump proteins are Darier disease and Hailey-Hailey disease, which show clinicopathological overlaps and develop both keratinizing and blistering skin lesions. Finally, gene mutations in epidermal keratins cause epidermolysis bullosa simplex, epidermolytic ichthyosis, superficial epidermolytic ichthyosis, epidermolytic palmoplantar keratoderma and pachyonychia congenita/focal palmoplantar keratoderma, which show thickening of the palms and soles with underlying blister formation. In general, responsible proteins for diseases developing both keratinizing and blistering conditions are adhesion molecules, calcium pump proteins and keratins, but not connexins, cornified cell envelop proteins, enzymes or inhibitors. It is still unknown how particular keratinizing diseases develop blisters and vice versa., (© 2012 John Wiley & Sons A/S.)

Pathogenic mutations have now been described in ten different desmosomal proteins: plakophilin 1 (PKP1) and 2 (PKP2); desmoplakin; plakoglobin; desmoglein 1, 2, and 4; desmocollin 2, and 3 corneodesmosin. Nevertheless, the first report of an inherited desmosomal gene disorder, published in 1997, involved loss-of-function mutations on both alleles of PKP1, the PKP1 gene. Loss of PKP1 expression in human skin leads to skin erosions and crusting, notably with perioral fissuring as well as palmoplantar hyperkeratosis with painful cracking of the skin. Other more variable features include abnormalities of ectodermal development with growth delay, hypotrichosis or alopecia, hypohidrosis, and nail dystrophy. In contrast to some other inherited disorders of desmosomes, there is no cardiac pathology in individuals with PKP1 mutations since it is not expressed in the heart. The collection of clinical features in individuals with PKP1 mutations has been termed ectodermal dysplasia-skin fragility (ED-SF) syndrome. This genodermatosis is classified as a suprabasal form of epidermolysis bullosa simplex and thus far there have been 10 published cases. Skin biopsy shows acanthosis, acantholysis, and a reduced number of small, poorly formed desmosomes. Loss of PKP1 expression results in an integral weakness within the desmosomal plaque, leading to desmosomal detachment and cell-cell separation. Thus, the clinicopathologic features attest to the significant role of PKP1 in stabilization of desmosome structure and function, predominantly in the spinous layers of the epidermis. This article reviews the clinical, structural, and molecular pathology of this genetic disorder of desmosomes.

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening adverse drug reactions characterized by massive epidermal necrosis, in which the specific danger signals involved remain unclear. Here we show that blister cells from skin lesions of SJS-TEN primarily consist of cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells, and both blister fluids and cells were cytotoxic. Gene expression profiling identified granulysin as the most highly expressed cytotoxic molecule, confirmed by quantitative PCR and immunohistochemistry. Granulysin concentrations in the blister fluids were two to four orders of magnitude higher than perforin, granzyme B or soluble Fas ligand concentrations, and depleting granulysin reduced the cytotoxicity. Granulysin in the blister fluids was a 15-kDa secretory form, and injection of it into mouse skin resulted in features mimicking SJS-TEN. Our findings demonstrate that secretory granulysin is a key molecule responsible for the disseminated keratinocyte death in SJS-TEN and highlight a mechanism for CTL- or NK cell--mediated cytotoxicity that does not require direct cellular contact.

Sarco(endo)plasmic reticulum Ca2+-ATPase isoform 2 (SERCA2) pumps belong to the family of Ca2+-ATPases responsible for the maintenance of calcium in the endoplasmic reticulum. In epidermal keratinocytes, SERCA2-controlled calcium stores are involved in cell cycle exit and onset of terminal differentiation. Hence, their dysfunction was thought to provoke impaired keratinocyte cohesion and hampered terminal differentiation. Here, we assessed cultured keratinocytes and skin biopsies from a canine family with an inherited skin blistering disorder. Cells from lesional and phenotypically normal areas of one of these dogs revealed affected calcium homeostasis due to depleted SERCA2-gated stores. In phenotypically normal patient cells, this defect compromised upregulation of p21(WAF1) and delayed the exit from the cell cycle. Despite this abnormality it failed to impede the terminal differentiation process in the long term but instead coincided with enhanced apoptosis and appearance of chronic wounds, suggestive of secondary mutations. Collectively, these findings provide the first survey on phenotypic consequences of depleted SERCA-gated stores for epidermal homeostasis that explain how depleted SERCA2 calcium stores provoke focal lesions rather than generalized dermatoses, a phenotype highly reminiscent of the human genodermatosis Darier disease.

Bullous pemphigoid (BP) is a subepidermal blistering disease associated with autoantibodies against two hemidesmosomal proteins, BP180 and BP230. Numerous inflammatory cells infiltrate the upper dermis in BP. We have previously shown by passive transfer studies that Abs to the ectodomain of murine BP180 are capable of triggering blisters in mice that closely mimic human BP. Experimental BP depends on complement activation and neutrophil infiltration. In the present study, we investigated the relative contribution of neutrophils, mast cells (MCs), macrophages (Mphi), and lymphocytes and their functional relationship in the immunopathogenesis of this disease model by using mice deficient in these cells. Wild-type, T cell-deficient, and T and B cell-deficient mice injected intradermally with pathogenic anti-murine BP180 IgG exhibited extensive subepidermal blisters. In contrast, mice deficient in neutrophils, MCs, and Mphi were resistant to experimental BP. MCs play a major role in neutrophil recruitment into the dermis. Furthermore, Mphi-mediated neutrophil infiltration depends on MC activation/degranulation.

The bli-1 gene of Caenorhabditis elegans has been previously described as a mutation which disrupts the structure of the adult-stage cuticle causing the formation of fluid-filled blisters. We investigated the blistering phenotype exhibiting n361 allele and observed a gradual blister formation in adult nematodes. In the course several fine changes occurred including a high electron density granulous material filling the intermediate layer, alterations on struts structure, and finally the total disappearance of the fibrous and basal layers. With the ethanolic phosphotungstic acid technique (E-PTA), which localizes basic proteins, reaction product was observed in the cortical layer of the wild strain, whereas in the mutant strain an irregular labelling pattern was observed in this region. The granulous material inside the intermediate layer of the mutant strain showed also a strong reaction. An imidazole-buffered osmium tetroxide solution was used to visualize lipids at ultrastructural level, however no dense product was detected in the cuticle of both strains of C. elegans. Based on these results we postulated that the blistering phenotype is due to an altered function of bli-1 gene, which is probably enzymatic.

A 450-kDa human epidermal autoantigen was originally identified as a protein that reacted with the serum from an individual with a subepidermal blistering disease. Molecular cloning of this protein has now shown that it contains 5065 amino acids and has a molecular mass of 552 kDa. As reported previously this protein, which we call epiplakin, belongs to the plakin family, but it has some very unusual features. Epiplakin has 13 domains that are homologous to the B domain in the COOH-terminal region of desmoplakin. The last five of these B domains, together with their associated linker regions, are particularly strongly conserved. However, epiplakin lacks a coiled-coil rod domain and an amino-terminal domain, both of which are found in all other known members of the plakin family. Furthermore, no dimerization motif was found in the sequence. Thus, it is likely that epiplakin exists in vivo as a single-chain structure. Epitope mapping experiments showed that the original patient's serum recognized a sequence unique to epiplakin, which was not found in plectin. Immunofluorescence staining revealed the presence of epiplakin in whole sheets of epidermis and esophagus, in glandular cells of eccrine sweat and parotid glands and in mucous epithelial cells in the stomach and colon.

Integrins alpha3beta1 and alpha6beta4 are abundant receptors on keratinocytes for laminin-5, a major component of the basement membrane between the epidermis and the dermis in skin. These integrins are recruited to distinct adhesion structures within keratinocytes; alpha6beta4 is present in hemidesmosomes, while alpha3beta1 is recruited into focal contacts in cultured cells. To determine whether differences in localization reflect distinct functions of these integrins in the epidermis, we studied skin development in alpha3beta1-deficient mice. Examination of extracellular matrix by immunofluorescence microscopy and electron microscopy revealed regions of disorganized basement membrane in alpha3beta1-deficient skin. Disorganized matrix was first detected by day 15.5 of embryonic development and became progressively more extensive as development proceeded. In neonatal skin, matrix disorganization was frequently accompanied by blistering at the dermal-epidermal junction. Laminin-5 and other matrix proteins remained associated with both the dermal and epidermal sides of blisters, suggesting rupture of the basement membrane itself, rather than detachment of the epidermis from the basement membrane as occurs in some blistering disorders such as epidermolysis bullosa. Consistent with this notion, primary keratinocytes from alpha3beta1-deficient skin adhered to laminin-5 through alpha6 integrins. However, alpha3beta1-deficient keratinocytes spread poorly compared with wild-type cells on laminin-5, demonstrating a postattachment requirement for alpha3beta1 and indicating distinct roles for alpha3beta1 and alpha6beta4. Our findings support a novel role for alpha3beta1 in establishment and/or maintenance of basement membrane integrity, while alpha6beta4 is required for stable adhesion of the epidermis to the basement membrane through hemidesmosomes.

Blistering skin diseases represent a genetically and biologically heterogeneous group of pathologic conditions with attenuated epithelial adhesion in the skin or in mucosal surfaces. Investigations on genetic blistering disorders with ultrastructural analysis, determination of candidate genes, and isolation and characterization of the target proteins have had a major impact on our understanding of normal epithelial-mesenchymal interactions and epithelial cell adhesion in general. A higf1p4gree of molecular heterogeneity underlies the different pathological phenotypes, and certain genotype-phenotype correlations are starting to emerge. Accumulating data on the molecular basis of different blistering diseases have already disclosed ample new information on the physiological functions of many of the molecular components of the dermal-epidermal junction, and we expect a rapid expansion of knowledge on the field when genotype-phenotype correlations of more patients are discerned.