Novel pathogenic variants in an Indian cohort with epidermolysis bullosa: Expanding the genotypic spectrum

BackgroundEpidermolysis bullosa (EB) is a genodermatosis characterized by skin fragility and blisters with variable severity. Patients with Dystrophic EB (DEB) or Junctional EB (JEB) mainly present to clinic due to greater functional impairment. Pathogenic sequence variations in COL7A1 are implicated in DEB.ObjectiveWe have tried to decipher the molecular spectrum and genotype phenotype correlation of 21 Indian patients with EB.MethodsNext generation sequencing (NGS) was performed to determine the pathogenic variants. Sanger sequencing was also done for validation of the variants in eleven individuals.ResultsPathogenic variants were detected in 20 individuals (diagnostic yield of 95%). Majority of them (90%) had sequence variation in COL7A1 while two had pathogenic variants in ITGB4 and KRT14 respectively. Out of the 18 patients confirmed to have DEB, 3 had Dominant DEB (DDEB) whereas 15 patients had Recessive DEB (RDEB). Amongst 23 sequence variations identified, 12 were found to be novel (3 were missense, 5 were premature termination codon variants while 4 were splice-site changes).ConclusionGenotype phenotype correlation was noted with milder manifestations in those with dominant inheritance types. Exact molecular diagnosis can be ascertained by NGS in majority of cases.     

Generalized,severe epidermolysis bullosa simplex caused by a Keratin 5 p.E477K mutation

Epidermolysis bullosa simplex (EBS) is a skin fragility disorder resulting from mutations of structural proteins in the epidermis. We provide a brief report of long‐term survival and reproduction in a mother with EBS due to keratin 5 (KRT5) c.1429G > A (p.E477K) mutation, which causes a particularly severe form of the disease.     

Next-generation sequencing through multigene panel testing for the diagnosis of hereditary epidermolysis bullosa in Chinese population

Epidermolysis bullosa (EB) is a heritable blistering disorder. We performed a next-generation sequencing-based multigene panel test and successfully predicted 100% of the EB types, including, 36 EB simplex (EBS), 13 junctional EB (JEB), 86 dystrophic EB (DEB), and 3 Kindler EB. Chinese JEB and recessive DEB (RDEB) patients have relatively mild phenotypes; for severe type separately accounts for 45.5% and 23.8%, respectively. We identified 96 novel and 49 recurrent pathogenic variants in 11 genes, although we failed to detect the second mutation in one JEB and five RDEB patients. We identified one novel p.E475K mosaic mutation in the clinically normal mother of one out of 13 EBS patients with KRT5 mutations, one recurrent p.G2034R mosaic mutation, and one novel p.G2043R mosaic mutation in the clinically normal relatives of two out of 19 dominant DEB patients. This study shows that next-generation technology could be an effective tool in diagnosing EB.     

获得性大疱性表皮松解症基底膜自身抗体靶抗原的定位研究

目的 探讨获得性大疱性表皮松解症(EBA)基底膜带自身抗体(BMZ—Ab)的靶抗原及其定位情况。方法 用免疫印迹(IB)、盐裂皮肤间接免疫荧光(IIF)、间接免疫电镜(IIEM)等方法检测6例EBA血清中。IgG型及IgA型BMZ—Ab识别的真表皮抗原以及抗原定位情况。结果 6例EBA血清中IgG型BMZ—Ab均结合真皮提取物中290ku蛋白，3例同时伴有结合290ku蛋白的IgA型BMZ—Ab。盐裂皮肤IIF显示BMZ真皮侧IgG线状沉积，IIEM示金颗粒沉积于BMZ致密下层，即真皮锚原纤维的Ⅶ型胶原处。结论 位于BMZ致密下层的Ⅶ型胶原是EBA中BMZ-Ab的特异性靶抗原，Ⅶ型胶原上的抗原表位可被EBA血清中IgG及IgA型BMZ—Ab识别。     

Epidermolysis bullosa herpetiformis (Dowling-Meara type) exhibits ultrastructural derangement of tonofilaments and desmosomes

Ultrastructural and immunohistochemical studies of clinically intact skin obtained from three severe neonatal cases of epidermolysis bullosa herpetiformis (Dowling-Meara type) demonstrated disorders in the assembly of keratin intermediate filaments and desmosomes of the keratinocytes. During mitosis, K5- and K14-positive and K1- and K10-negative tonofilaments were disrupted and formed spherical bodies associated with intracytoplasmic desmosomes by invagination of the desmosomes and the adjacent plasma membrane. During the invagination process, destructive changes in the internalized membrane were noted. These were accompanied by gradual loss of reactivity with a monoclonal antibody ZK31, which detected plasma membrane adjacent to the attachment plaques of desmosomes. However, the reactivity of the attachment plaques of the internalized desmosomes for desmoplakins and desmoglein did not decline during the process of internalization. In the suprabasal layers of the epidermis, filamentous substructures and K1 and K10 appeared at the periphery of the spherical bodies. Simultaneously, the desmosomes that were sparsely located in the lower epidermis, increased in number as cell differentiation progressed. Thus, the keratinocytes attained an almost normal appearance with respect to tonofilaments and desmosomes by the time they reached the upper layer of the epidermis. These findings may be relevant to the mechanism responsible for the clinical appearance of the herpetiform blisters in epidermolysis bullosa herpetiformis, which are also characterized by spontaneous involution during childhood or when exposed to high ambient temperatures.Part of this work was presented at the annual meeting of the Japanese Society for Ultrastructural Cutaneous Biology, 12 May 1990, Tokushima, Japan, at the joint meeting of the Society for Cutaneous Ultrastructure Research and the Japanese Society for Ultrastructural Cutaneous Biology, 23–25 May 1991, Vienna, Austria, and at the sixth Conference on Disorders of Keratinization, 6 July 1991, Tokyo, Japan     

Empfehlungen für die Anwendung der Immunapherese bei der Therapie bullöser Autoimmundermatosen

The etiology of epidermolysis bullosa acquisita (EBA) is unknown. EBA may be associated with other autoim‐mune systemic diseases; it also has been described in connection with different malignant tumors, showing complete remission after successful treatment of the tumor.In such cases, EBA may be regarded as a paraneo‐plastic dermatosis. We detected a highly differentiated neuroendocrine pancreatic cancer in a 78‐year‐old woman with EBA. Even thought her tumor was completely removed and the patient has been disease‐free for over seven years, a complete regression of her autoimmune bullous dermatosis could not be induced. By using intravenous immunoglobulins in combination with mycophenolate mofetil, further blister formation could be ameliorated.     

The molecular basis for inherited bullous diseases

In the past 5 years enormous progress have been made in our understanding of the molecular basis for a number of inherited skin diseases characterized by easy blistering of the skin and the mucous membranes after minor physical trauma. This increased fragility of the skin or its appendages is due to molecular defects in genes coding for different intra- and extracellular structural proteins which are responsible for mechanical strength at their sites of expression. These diseases encompass the group of epidermolysis bullosa and disorders of cornification such as bullous forms of ichthyosis, palmoplantar keratoderma, and pachyonychia congenita. On the basis of clinical, morphological, and ultrastructural observations the epidermolysis bullosa group has been divided into three major categories. In epidermolysis bullosa simplex blister formation appears within the basal cell layer of the epidermis, and many mutations have been found in the genes of keratin 5 and 14 which are both expressed in basal keratinocytes. Epidermolytic hyperkeratosis leads to an epidermal separation in the suprabasal cell layers. In these patients numerous point mutations have now been described in the suprabasally expressed genes of keratin 1 and 10. In ichthyosis bullosa of Siemens blisters occur in the more upper suprabasal epidermis coincidental with the expression of keratin 2e, and mutations have been detected in the corresponding gene. In epidermolytic palmoplantar hyperkeratosis the suprabasal epidermal splitting is restricted to palms and soles of the patient. In keratin 9, which reveals such an exclusive expression pattern, molecular defects have indeed been recognized. Most recently in two different clinical subtypes of pachyonychia congenita, which is characterized by defective nails and focal palmoplantar hyperkeratosis, point mutations have been found in the genes coding for keratins 6, 16, and 17. In junctional epidermolysis bullosa the separation takes place within the dermal-epidermal basement membrane at the level of the lamina lucida, and mutations have been found in three genes coding for different laminin chains, in the ₄ gene of ₆₄ integrin, and in the gene of collagen XVII. In dystrophic epidermolysis bullosa the tissue separation occurs beneath the basement membrane within the papillary dermis at the level of the anchoring fibrils, and several mutations have been identified in the collagen VII gene. The rapid unraveling of molecular defects in these disabling or even lethal inherited skin diseases makes possible a more precise and earlier prenatal diagnosis, creates new options for suitable therapeutic regimens, and even offers the hope of curing these diseases by means of somatic cell gene therapy.Abbreviations BM Basement membrane - BPAg Bullous pemphigoid antigen - DEB Dystrophic epidermolysis bullosa - EB Epidermolysis bullosa - EBS Epidermolysis bullosa simplex - EHK Epidermolytic hyperkeratosis - EPPK Epidermolytic palmoplantar keratoderma - IBS Ichthyosis bullosa of Siemens - JEB Junctional epidermolysis bullosa - KIF Keratin intermediate filaments - NC Noncollagenous domain - NEPPK Nonepidermolytic palmoplantar keratoderma - PC Pachyonychia congenita     

Pneumatised superior turbinate: a common anatomic variation?

Summary Anatomic variations are important in preendoscopic CT evaluation of the paranasal sinuses. In this study, we investigated whether the superior turbinate could become pneumatised like the middle turbinate, pneumatisation of which is well-known. Images of 52 patients who underwent CT examination prior to endoscopic sinus surgery and who had normally aerated posterior ethmoidal cells and an unobscured nasal cavity were retrospectively evaluated. The patients were 12–68 years old (median age, 35 years); 28 were women and 24 were men. Pneumatisation of the superior turbinates was graded in two groups as minimal or marked. Pneumatisation was evident in 25 patients (48%). 13 unilateral (25%), 8 bilateral (15%) pneumatisations were detected in the group graded as minimal, whereas 1 unilateral and 3 bilateral pneumatisations were present in the markedly (8%) pneumatised group of patients. Superior turbinates were seemingly aerated through the posterior ethmoid cells. The superior turbinates can be pneumatised as the middle turbinate is a not frequent anatomic variation that should be taken into account in preendoscopic CT evaluation of the paranasal sinuses.

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La pneumatisation du cornet nasal supérieur : une variation anatomique courante ?

Résumé Les variations anatomiques sont importantes à connaitre dans le cadre du bilan tomodensitométrique précédant une chirurgie endoscopique des sinus paranasaux. Dans cette étude, nous avons recherché si le cornet nasal supérieur pouvait être pneumatisé comme l'est le cornet nasal moyen, entité anatomique bien connue. Les images de 52 patients ayant eu une tomodensitométrie avant chirurgie endoscopique et montrant des cellules ethmoïdales postérieures normalement pneumatisées et une cavité nasale nonopaque, ont été évaluées rétrospectivement. Les patients, 28 femmes et 24 hommes, étaient âgés de 12 à 68 ans (moyenne : 35 ans). La pneumatisation du cornet nasal supérieur a été classée en deux groupes; minime et prononçée. Cette pneumatisation était patente chez 25 patients (48 %). Treize pneumatisations unilatérales (25 %) et 8 pneumatisations bilatérales (15 %) furent retrouvées dans le groupe présentant une pneumatisation minime alors que 1 pneumatisation unilatérale et 3 bilatérales (8 %) étaient présentes dans le groupe dont la pneumatisation était plus marquée. Les cornets nasaux supérieurs semblaient être aérés par les cellules ethmoïdales postérieures. Les cornets nasaux supérieurs peuvent être pneumatisés, comme le sont les cornets nasaux moyens, avec une fréquence non-exceptionnelle. Cette variation anatomique mérite d'être prise en considération dans le bilan tomodensitométrique précédant toute chirurgie endoscopique des sinus paranasaux.

     

Ultrastructural Features of Epidermolysis Bullosa

Epidermolysis bullosa (EB), a heterogeneous group of hereditary diseases, varies in mode of inheritance, extent, severity, and presence or absence of scarring and dystrophy. Fourteen cases (13 in infants and 1 in a young adult) were studied. Subtyping by ultrastructural findings in normal and blistered skin biopsies was as follows: EB simplex (2), EB letalis (3), EBD dominant (2), and EBD recessive (7). One case diagnosed as recessive dystrophic by electron microscopy (EM) followed a benign course with little scaring and was re-classified clinically and after reviewing the EM as dominant dystrophic. Defining the level of bulla formation by EM allowed accurate diagnosis of subtypes. In 6 patients with EBD recessive, normal and bullous skin showed collagenolysis and no anchoring fibrils. In patients with EBD dominant, rudimentary fibrils were noted in normal skin. Whether absence of anchoring fibrils is primary or secondary in these two types and the role of collagenolysis remain unresolved.     

鼠抗人单克隆抗体LH7：2在营养不良型大疱性表皮松解症诊断中的应用

目的 探讨鼠抗人单克隆抗体LH7：2诊断营养不良型大疱性表皮松解症的意义。方法 采用间接免疫荧光法对临床诊断为营养不良型大疱性表皮松解症（DEB）,分别来源于3个不同家系各1名患者,包括2名显性遗传型营养不良型大疱性表皮松解症（dominant DEB,DDEB)和1名隐性遗传型营养不良型大疱性表皮松解症（recessive DEB,RDEB)进行皮肤基底膜带（BMZ）Ⅶ型胶原检测,同时选择单纯型大疱性表皮松解症（EBS）、大疱性类天疱疮及正常人各1名做对照。结果 3名对照BMZ免疫荧光阳性,2名DDEB荧光均减弱,RDEB荧光阴性。结论 鼠抗人单克隆抗体LH7：2诊断营养不良性大疱性表皮松解症有重要意义。