A Case of Annular Epidermolytic Ichthyosis Resulting from a de Novo Mutation, p.I479T, in Keratin 1 Gene.
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SUBMITTER: Chen L
PROVIDER: S-EPMC8208282 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Annular epidermolytic ichthyosis (AEI; Online Mendelian Inheritance in Man [OMIM]# 607602) is a rare subtype of epidermolytic ichthyosis that is characterized by polycyclic, migratory erythematous and scaly plaques. It typically results from dominant mutations in the keratin 1 or keratin 10 genes. We present the case of a 5-year-old girl who developed intermittent eruptions of pink, round, scaly, migratory plaques with palmoplantar keratoderma and was originally diagnosed with erythrokeratodermia variabilis et progressiva (EKVP). Genetic analysis revealed a c.1436T>C transition mutation in the keratin 1 gene, and histopathology showed epidermolysis and hyperkeratosis, confirming the diagnosis of AEI.
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Project description:Mutations in keratin genes underlie a variety of epidermal and nonepidermal cell-fragility disorders, and are the genetic basis of many inherited palmoplantar keratodermas (PPKs). Epidermolytic PPK (EPPK) is an autosomal dominant disorder that can be due to mutations in the keratin 1 gene, KRT1. Epidermolytic ichthyosis (EI), the major keratinopathic ichthyosis, is characterized by congenital erythroderma, blistering and erosions of the skin. Causative mutations in KRT1 and KRT10 have been described, with PPK being present primarily in association with the former. We report four unrelated cases (one with sporadic EI and three with autosomal dominant PPK), due to two novel and two recurrent KRT1 mutations. Mutations in KRT1 are not only scattered throughout the keratin 1 protein, as opposed to being clustered, but can result in a range of phenotypes as further confirmed by these mutations, giving a complex genotype/phenotype pattern.
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Project description:Epidermolytic ichthyosis (EI) is a rare disorder of cornification caused by mutations in KRT1 and KRT10, encoding two suprabasal epidermal keratins. Because of the variable clinical features and severity of the disease, histopathology is often required to correctly direct the molecular analysis. EI is characterized by hyperkeratosis and vacuolar degeneration of the upper epidermis, also known as epidermolytic hyperkeratosis, hence the name of the disease. In the current report, the authors describe members of 2 families presenting with clinical features consistent with EI. The patients were shown to carry classical mutations in KRT1 or KRT10, but did not display epidermolytic changes on histology. These observations underscore the need to remain aware of the limitations of pathological features when considering a diagnosis of EI.
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Project description:Bullous congenital ichthyosiform erythroderma (BCIE) is characterized by blistering and erythroderma in infancy and by erythroderma and ichthyosis thereafter. Epidermolytic hyperkeratosis is a hallmark feature of light and electron microscopy. Here we report on four individuals from two families with a unique clinical disorder with histological findings of epidermolytic hyperkeratosis. Manifesting erythema and superficial erosions at birth, which improved during the first few months of life, affected individuals later developed palmoplantar hyperkeratosis with patchy erythema and scale elsewhere on the body. Three affected individuals exhibit dramatic episodic flares of annular, polycyclic erythematous plaques with scale, which coalesce to involve most of the body surface. The flares last weeks to months. In the interim periods the skin may be normal, except for palmoplantar hyperkeratosis. Abnormal keratin-filament aggregates were observed in suprabasal keratinocytes from both probands, suggesting that the causative mutation might reside in keratin K1 or keratin K10. In one proband, sequencing of K1 revealed a heterozygous mutation, 1436T-->C, predicting a change of isoleucine to threonine in the highly conserved helix-termination motif. In the second family, a heterozygous mutation, 1435A-->T, was found in K1, predicting an isoleucine-to-phenylalanine substitution in the same codon. Both mutations were excluded in both a control population and all unaffected family members tested. These findings reveal that a clinical phenotype distinct from classic BCIE but with similar histology can result from K1 mutations and that mutations at this codon give rise to a clinically unique condition.
| S-EPMC1377790 | biostudies-other
Project description:BackgroundSuperficial epidermolytic ichthyosis (SEI), known as ichthyosis bullosa of Siemens (IBS; OMIM No. 146800) before, is a type of keratinopathic ichthyosis due to the KRT2 mutations (NM_000423.3; OMIM No. 600194). Here, we report the first case of SEI caused by a KRT2 mosaic mutation.MethodsWe presented the clinical data of a 5-year-old Chinese boy who suffered from SEI. The histopathological examination and immunofluorescence were performed to rule out immunobullous skin diseases and diseases with subepidermal blisters. Genomic DNA samples were extracted from the lesion tissue and next-generation sequencing was performed. We also confirmed the variant allele frequency (VAF) in different tissues by an Ultra-Deep Sequencing technology.ResultsThe patient presented with blisters on the lower extremities and linear, superficially hyperkeratotic lesions. Immunofluorescence of IgG, IgA, IgM, C3, C4, and C1q were negative, and the histopathological results showed intraepidermal blisters containing lymphocytes and eosinophils. A heterozygous missense mutation, c.G1459A (p. Glu487Lys), in exon 7 of the KRT2 gene was detected at a 31.17% allele frequency. The same mutation p. Glu487Lys has been described several times in the literature.ConclusionThus, in our patient, the mosaic mutation explains the blaschkoid ichthyosiform phenotype. To our knowledge, this is the first case of SEI with a KRT2 mosaic mutation.
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Project description:Abstract Introduction: Progressive osseous heteroplasia (POH) is a rare bone disorder characterized by heterotopic ossification in the skin and muscles, resulting in contractures of the joints and progressive loss of function. Whereas 60-70% of the POH patients have paternally inherited inactivating mutations in GNAS gene, the remaining 30-40% harbor no specific etiologies. FAM111B gene mutations, located on chromosome 11q12.1, cause POIKTMP (hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis), a rare autosomal dominant disorder with high frequency of de novo missense mutations, which are believed to cause extensive fibrosis and adiposis of many tissues, though the exact mechanism is unknown. To our knowledge there are no reports of FAM111B associated with POH. Case: We describe a 15-year-old African American boy who presented with generalized calcific nodules, contractures, and muscle weakness leading to immobility, beginning at the age of 6 years. Cutaneous exam showed generalized hard nodules varying from small to plaque-like ulcerated erupted skin lesions. Biochemical evaluation revealed 25(OH) vitamin D insufficiency (20 ng/mL), and normal levels of parathyroid hormone, FGF-23, alkaline phosphatase, calcium, and phosphorus. Skeletal survey radiographs showed extensive heterotopic ossification involving soft tissues and muscles surrounding the bilateral humeri, ulnae, femurs, and bilateral tibias/fibulas. Computed tomography of the chest, abdomen, and pelvis showed extensive muscle ossifications involving right latissimus dorsi, left scalene, bilateral pectoralis and external oblique abdominal, right iliacus, bilateral gluteal, left adductor, and left hamstring. There was also an involvement of the subcutaneous tissues of the right upper back and left lower quadrant of the abdomen, left posterior sacral region, bilateral hips, and the fascia superficial to the erector spinae muscles with no abnormal ossifications in the bones. The clinical and radiographic findings were consistent with POH. Whole Exome Sequencing revealed a de novo heterozygous frameshift mutation in FAM111B (OMIM # 615584) of c.1462delT (p.Cys488Valfs*21) variant, causing replacement of C-terminal region with 21 alternative amino acids. Multiple previously reported disease-associated variants appear to localize within the same domain, supporting the functional importance of this region, though none have been previously associated with POH. Thus, we consider this variant to be pathogenic. Conclusion: This is the first case of POH caused by a mutation in FAM111B gene. Whether POH phenotype could be explained by mutations in FAM111B gene traditionally reserved for POIKTMP remains unclear. Further evaluations are necessary to fully elucidate this finding and potential mechanism by which the FAM111B gene mutation contributes to POH.
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Project description:Superficial epidermolytic ichthyosis (SEI) is an autosomal dominant inherited ichthyosis. SEI is caused by mutations in KRT2 and frequently shows erythroderma and widespread blistering at birth. We report the clinical manifestations of two patients from a Japanese family with SEI caused by a hotspot mutation, p.Glu487Lys, in KRT2. In addition, we summarize previous reports on SEI patients with the identical mutation. One of the two patients had disease onset at the age of 7 months. The other patient's age of onset is unknown, but it was in childhood. Neither of the two patients showed erythroderma. To perform deep phenotyping, we studied the age of onset and the frequency of erythroderma in 34 reported SEI cases with the p.Glu487Lys mutation, including the present cases. Among the cases with sufficient clinical information, 44.4% of the cases that were due to p.Glu487Lys in KRT2 occurred at birth. Erythroderma was observed in 11.1% of the cases with p.Glu487Lys in KRT2.
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Project description:Ichthyoses are a heterogeneous group of inherited cornification disorders characterized by generalized dry skin, scaling and/or hyperkeratosis. Ichthyosis vulgaris is the most common form of ichthyosis in humans and caused by genetic variants in the FLG gene encoding filaggrin. Filaggrin is a key player in the formation of the stratum corneum, the uppermost layer of the epidermis and therefore crucial for barrier function. During terminal differentiation of keratinocytes, the precursor profilaggrin is cleaved by several proteases into filaggrin monomers and eventually processed into free amino acids contributing to the hydration of the cornified layer. We studied a German Shepherd dog with a novel form of ichthyosis. Comparing the genome sequence of the affected dog with 288 genomes from genetically diverse non-affected dogs we identified a private heterozygous variant in the ASPRV1 gene encoding "aspartic peptidase, retroviral-like 1", which is also known as skin aspartic protease (SASPase). The variant was absent in both parents and therefore due to a de novo mutation event. It was a missense variant, c.1052T>C, affecting a conserved residue close to an autoprocessing cleavage site, p.(Leu351Pro). ASPRV1 encodes a retroviral-like protease involved in profilaggrin-to-filaggrin processing. By immunofluorescence staining we showed that the filaggrin expression pattern was altered in the affected dog. Thus, our findings provide strong evidence that the identified de novo variant is causative for the ichthyosis in the affected dog and that ASPRV1 plays an essential role in skin barrier formation. ASPRV1 is thus a novel candidate gene for unexplained human forms of ichthyoses.
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Project description:Congenital adrenal hyperplasia, one of the most frequent autosome recessive disorders, is caused by defects in steroidogenic enzymes involved in the cortisol biosynthesis. Approximately 95% of the cases are caused by abnormal function of the 21-hydroxylase enzyme. This deficiency leads to androgen excess, consequently, to virilization and rapid somatic growth with accelerated skeletal maturation. Mutations in CYP21A2 are responsible for different forms of 21-hydroxylase deficiency. Mild impairment in the enzymatic activity causes the non-classic or late-onset congenital adrenal hyperplasia that is observed with a prevalence of 1 in 1000 subjects in different populations. The present paper describes a de novo mutation that occurred in the paternal meiosis. The child, who was conceived by in vitro fertilization, presented with precocious puberty and diagnosed with non-classical 21-hydroxylase deficiency. DNA sequencing showed the compound heterozygosis for a de novo CYP21A1P/A2 chimeric gene and the p.Val281Leu mutation inherited from her mother, who was heterozygous for the mutation. The chimeric gene showed pseudogene-derived sequence from 5'-end to intron 3 and CYP21A2 sequences from intron 3 to 3'-end of the gene. Sequencing analysis of the father did not show any mutation. The multiplex ligation-dependent probe amplification (MLPA) assay did not indicate loss of DNA discarding gene deletion but confirmed the chimeric gene. In addition, supernumerary copies of CYP21A1P were observed for both parents and for the affect child. Since paternity has been confirmed, those results suggest that a de novo large gene conversion in the paternal meiosis could have occurred by misalignment of alleles bearing different copy numbers of genes in CYP21 locus.
| S-EPMC5471403 | biostudies-literature
Project description:Keratins are heteropolymeric proteins that form the intermediate filament cytoskeleton in epithelial cells. The common basic structure of all keratins is organized in a central ?-helical rod domain flanked by nonhelical, variable head and tail regions. Most mutations in keratins are found in the central ?-helical rod domain. Keratin 9 (K9) is expressed only in the suprabasal layers of palmoplantar epidermis. Mutations in the keratin 9 gene (KRT9) have been shown to cause epidermolytic palmoplantar keratoderma (EPPK; OMIM 144200), an autosomal dominant genodermatosis characterized clinically by diffuse hyperkeratosis limited to the palms and soles, and histologically by epidermolysis in suprabasal layers of the epidermis.To elucidate the genetic basis of EPPK in five Pakistani families.Using microsatellite markers localized to the areas around the type I keratin gene cluster on chromosome 17q21, genotyping of these families was performed, followed by sequencing of the KRT9 gene.The analysis resulted in the identification of two novel (p.M157K and p.Y454H) and two recurrent (p.M157T and p.R163Q) mutations in the KRT9 of all five families. All mutations occurred within the highly conserved helix initiation or termination motif of K9.The affected members of all five families possess mutations in the KRT9 gene that severely affect heterodimer formation with the type II keratin partner. The results of our study further underscore the crucial role of K9 protein in the palmoplantar epidermis.
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