Ichthyosis with confetti: clinics, molecular genetics and management

Inherited ichthyosis as a paradigm of rare skin disorders: Genomic medicine, pathogenesis, and management

Great advances have been made in the field of heritable skin disorders using next-generation sequencing (NGS) technologies (ie, whole-genome sequencing, whole-exome sequencing, whole-transcriptome sequencing, and disease-targeted multigene panels). When NGS first became available, the cost and lack of access to these technologies were limiting factors; however, with decreasing sequencing costs and the expanding knowledge base of genetic skin diseases, fundamental awareness of NGS has become prudent. The heritable ichthyoses comprise a genotypically and phenotypically heterogeneous group of monogenic keratinization disorders characterized by persistent scaling, with at least 55 distinct genes currently implicated in causing nonsyndromic and syndromic forms of the disease. By providing a simplified overview of available NGS techniques and applying them in the context of ichthyosis, one of the most common genodermatoses, we hope to encourage dermatologists to offer, when appropriate, genetic testing earlier in patients with unsolved presentations. With the aid of NGS, dermatologists can provide diagnostic certainty in cases of suspected genodermatoses and offer potentially life-changing genome-guided and targeted therapies as they become available.

Otological problems in ichthyosis: A literature review

BACKGROUND

Ichthyoses are a rare group of keratinization disorders characterized by scaling of the skin due to an impaired barrier function. Few studies have addressed ear involvement in patients with ichthyosis, although it is a probably underestimated aspect of the disease.

OBJECTIVE

This study aims to provide an overview of the otological manifestations in ichthyosis and propose specific treatment options.

METHODS

Articles were collected using PubMed, EMBASE, and Web of Science. A total of 53 articles were included in this literature review.

RESULTS

The most common ear problem in patients with ichthyosis is scale accumulation in the ear canals, which can lead to conductive hearing loss and increases the risk of ear infections. Furthermore, some types of ichthyosis are associated with outer ear malformations. Lastly, sensorineural hearing loss is common in syndromic forms of ichthyosis.

CONCLUSIONS

Otological problems are present in all types of ichthyoses and their treatment is challenging. The involvement of ear, nose, and throat specialists in the routine care of ichthyosis patients is essential for early identification and treatment of these manifestations. More research is needed to provide more insight into the otological problems in ichthyosis and to ameliorate treatment options.

Congenital Ichthyosis: Clinical and Genetic Characteristics of the Disease

Congenital ichthyosis is a group (almost 100 clinical variants) of rare genetic skin diseases caused by pathogenic changes in more than 50 genes. Clinical features of ichthyosis, regardless of its genotype, are dry skin, peeling, hyperkeratosis frequently accompanied with erythroderma. These patients have extremely low quality of life due to changes in appearance, discomfort due to itching and functional limitations (pain during walking, impaired hands motor skills and functions due to hyperkeratosis foci in functionally relevant areas), as well as impaired functions of various organs and systems in syndromic forms of disease. Patients need daily skin care and systemic medications. By now, there is no definitive treatment for ichthyosis. Diagnostic difficulties in determining the clinical forms of congenital ichthyosis are associated with their clinical heterogeneity and with similarity in external manifestations. Difficulties in differential diagnosis with other dermatoses are particularly crucial in case of syndromic forms of disease. This review presents the modern classification of ichthyoses, provides data on disease clinical and genetic variants, diagnostic algorithms, treatment methods for patients with this severe disease.

Revertant Mosaicism in Genodermatoses: Natural Gene Therapy Right before Your Eyes

Revertant mosaicism (RM) is the intriguing phenomenon in which nature itself has successfully done what medical science is so eagerly trying to achieve: correcting the effect of disease-causing germline variants and thereby reversing the disease phenotype back to normal. RM was molecularly confirmed for the first time in a genodermatosis in 1997, the genetic skin condition junctional epidermolysis bullosa (EB). At that time, RM was considered an extraordinary phenomenon. However, several important discoveries have changed this conception in the past few decades. First, RM has now been identified in all major subtypes of EB. Second, RM has also been identified in many other genodermatoses. Third, a theoretical mathematical exercise concluded that reverse mutations should be expected in all patients with a recessive subtype of EB or any other genodermatosis. This has shifted the paradigm from RM being an extraordinary phenomenon to it being something that every physician working in the field of genodermatoses should be looking for in every patient. It has also raised hope for new treatment options in patients with genodermatoses. In this review, we summarize the current knowledge on RM and discuss the perspectives of RM for the future treatment of patients with genodermatoses.

New developments in the molecular treatment of ichthyosis: review of the literature

Ichthyosis covers a wide spectrum of diseases affecting the cornification of the skin. In recent years, new advances in understanding the pathophysiology of ichthyosis have been made. This knowledge, combined with constant development of pathogenesis-based therapies, such as protein replacement therapy and gene therapy, are rather promising for patients with inherited skin diseases. Several ongoing trials are investigating the potency of these new approaches and various studies have already been published. Furthermore, a lot of case series report that biological therapeutics are effective treatment options, mainly for Netherton syndrome and autosomal recessive congenital ichthyosis. It is expected that some of these new therapies will prove their efficacy and will be incorporated in the treatment of ichthyosis.

Structural and functional foot disorders in patients with genodermatoses: a single-centre, retrospective chart review

Background

Skin lesions on the feet and foot deformities impair daily activities and decrease quality of life. Although substantial foot deformities occur in many genodermatoses, few reports have been published on this topic. Therefore, we performed a retrospective chart review to identify patients with genodermatoses and foot disorders. We included 16 patients, who were investigated clinically and with molecular biology.

Results

The following genodermatoses with foot deformities were detected: autosomal recessive congenital ichthyosis (ARCI, n = 7); palmoplantar keratodermas (PPKs, n = 6); ichthyosis follicularis, atrichia, and photophobia (IFAP, n = 1); ectrodactyly-ectodermal dysplasia-clefting (EEC, n = 1); and ichthyosis with confetti (IWC, n = 1). Foot problems not only varied in severity depending on the disease but also showed phenotypic heterogeneity among patients with the same condition. Foot deformities were most pronounced in patients with EEC (split foot) or IWC (contractures) and less severe in those with ARCI (clawed toes), IFAP (hollow feet), or PPK (no bone abnormalities in the feet).

Conclusion

Because a range of distinct genodermatoses involve foot abnormalities, early rehabilitation and other corrective measures should be provided to patients with foot involvement to improve gait and prevent/delay irreversible complications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02207-x.

Challenges in Treating Genodermatoses: New Therapies at the Horizon

Genodermatoses are rare inherited skin diseases that frequently affect other organs. They often have marked effects on wellbeing and may cause early death. Progress in molecular genetics and translational research has unravelled many underlying pathological mechanisms, and in several disorders with high unmet need, has opened the way for the introduction of innovative treatments. One approach is to intervene where cell-signaling pathways are dysregulated, in the case of overactive pathways by the use of selective inhibitors, or when the activity of an essential factor is decreased by augmenting a molecular component to correct disequilibrium in the pathway. Where inflammatory reactions have been induced by a genetically altered protein, another possible approach is to suppress the inflammation directly. Depending on the nature of the genodermatosis, the implicated protein or even on the particular mutation, to correct the consequences or the genetic defect, may require a highly personalised stratagem. Repurposed drugs, can be used to bring about a "read through" strategy especially where the genetic defect induces premature termination codons. Sometimes the defective protein can be replaced by a normal functioning one. Cell therapies with allogeneic normal keratinocytes or fibroblasts may restore the integrity of diseased skin and allogeneic bone marrow or mesenchymal cells may additionally rescue other affected organs. Genetic engineering is expanding rapidly. The insertion of a normal functioning gene into cells of the recipient is since long explored. More recently, genome editing, allows reframing, insertion or deletion of exons or disruption of aberrantly functioning genes. There are now several examples where these stratagems are being explored in the (pre)clinical phase of therapeutic trial programmes. Another stratagem, designed to reduce the severity of a given disease involves the use of RNAi to attenuate expression of a harmful protein by decreasing abundance of the cognate transcript. Most of these strategies are short-lasting and will thus require intermittent life-long administration. In contrast, insertion of healthy copies of the relevant gene or editing the disease locus in the genome to correct harmful mutations in stem cells is more likely to induce a permanent cure. Here we discuss the potential advantages and drawbacks of applying these technologies in patients with these genetic conditions. Given the severity of many genodermatoses, prevention of transmission to future generations remains an important goal including offering reproductive choices, such as preimplantation genetic testing, which can allow selection of an unaffected embryo for transfer to the uterus.

Case Report: Uncommon Association of ITGB4 and KRT10 Gene Mutation in a Case of Epidermolysis Bullosa With Pyloric Atresia and Aplasia Cutis Congenita

Background: Epidermolysis bullosa is a rare form of genodermatosis produced by different gene mutations. The junctional form of the disease (JEB-PA) can associate pyloric atresia, renal abnormalities, and aplasia cutis congenita.

Case Description: A case of a male preterm newborn with suspicion of digestive tube malformation at fetal ultrasound and who was born by cesarian section. At birth, he presented extensive cutaneous aplasia on the lower limbs and bilaterally under ears; outer ear agenesis; nasal septum hypoplasia; micrognathia; multiple blisters on the face, trunk, and limbs; lower limb deformities and absence of toe nails. Pathological examination following a surgical procedure with unfavorable outcome showed pyloric atresia, junctional form of epidermolysis bullosa and aplasia cutis congenita. Homozygous variants in two genes were identified: c.3111+1G>A in ITGB4 (class 5) and c.1498G>T in KRT10 (class 3).

Conclusion: The particularity of our case is the novel finding of a coincidental occurrence in the context of consaguinity of two mutations in the ITGB4 and KRT10 genes, and clinical characteristics of epidermolysis bullosa.

Report of a Novel ALOX12B Mutation in Self-Improving Collodion Ichthyosis with an Overview of the Genetic Background of the Collodion Baby Phenotype

Collodion baby is a congenital, transient phenotype encountered in approximately 70–90% of autosomal recessive congenital ichthyosis and is an important entity of neonatal erythroderma. The clinical outcome after this severe condition is variable. Genetic mutations of components of the epidermal lipoxygenase pathway have been implicated in the majority of self-improving collodion ichthyosis (SICI). In SICI, the shedding of the collodion membrane reveals clear skin or only mild residual manifestation of ichthyosis. Here we report the case of a girl born with a severe form of collodion baby phenotype, whose skin almost completely cleared within the first month of life. At the age of 3 years, only mild symptoms of a keratinization disorder remained. However, the severity of erythema and scaling showed mild fluctuations over time. To objectively evaluate the skin changes of the patient, we assessed the ichthyosis severity index. Upon sequencing of the ALOX12B gene, we identified a previously unreported heterozygous nonsense mutation, c.1607G>A (p.Trp536Ter) with the recurrent, heterozygous mutation c.1562A>G (p.Tyr521Cys). Thereby, our findings expand the genotypic spectrum of SICI. In addition, we summarize the spectrum of further genetic diseases that can present at birth as collodion baby, in particular the SICI.

Consensus recommendations for the use of retinoids in ichthyosis and other disorders of cornification in children and adolescents

Topical and systemic retinoids have long been used in the treatment of ichthyoses and other disorders of cornification. Due to the need for long-term use of retinoids for these disorders, often beginning in childhood, numerous clinical concerns must be considered. Systemic retinoids have known side effects involving bone and eye. Additionally, potential psychiatric and cardiovascular effects need to be considered. Contraceptive concerns, as well as the additive cardiovascular and bone effects of systemic retinoid use with hormonal contraception must also be deliberated for patients of childbearing potential. The Pediatric Dermatology Research Alliance (PeDRA) Use of Retinoids in Ichthyosis Work Group was formed to address these issues and to establish best practices regarding the use of retinoids in ichthyoses based on available evidence and expert opinion.

Types of congenital nonsyndromic ichthyoses

Congenital ichthyoses are a very heterogeneous group of diseases manifested by dry, rough and scaling skin. In all forms of ichthyoses, the skin barrier is damaged to a certain degree. Congenital ichthyoses are caused by various gene mutations. Clinical manifestations of the individual types vary as the patient ages. Currently, the diagnosis of congenital ichthyoses is based on molecular analysis, which also allows a complete genetic counseling and genetic prevention. It is appropriate to refer the patients to specialized medical centers, where the cooperation of a neonatologist, a pediatric dermatologist, a geneticist and other specialists is ensured.

First Case of KRT2 Epidermolytic Nevus and Novel Clinical and Genetic Findings in 26 Italian Patients with Keratinopathic Ichthyoses

Keratinopathic ichthyoses (KI) are a clinically heterogeneous group of keratinization disorders due to mutations in KRT1, KTR10, or KRT2 genes encoding keratins of suprabasal epidermis. Characteristic clinical features include superficial blisters and erosions in infancy and progressive development of hyperkeratosis. Histopathology shows epidermolytic hyperkeratosis. We describe the clinical, histopathological, and molecular findings of a series of 26 Italian patients from 19 unrelated families affected with (i) epidermolytic ichthyosis due to KRT1 or KRT10 mutations (7 and 9 cases, respectively); (ii) KTR10-mutated ichthyosis with confetti (2 cases); (iii) KRT2-mutated superficial epidermolytic ichthyosis (5 cases); and (iv) KRT10-mutated epidermolytic nevus (2 cases). Of note, molecular genetic testing in a third case of extensive epidermolytic nevus revealed a somatic missense mutation (p.Asn186Asp) in the KRT2 gene, detected in DNA from lesional skin at an allelic frequency of 25% and, at very low frequency (1.5%), also in blood. Finally, we report three novel dominant mutations, including a frameshift mutation altering the C-terminal V2 domain of keratin 1 in three familiar cases presenting a mild phenotype. Overall, our findings expand the phenotypic and molecular spectrum of KI and show for the first time that epidermolytic nevus can be due to somatic KRT2 mutation.

Recombination-induced revertant mosaicism in ichthyosis with confetti and loricrin keratoderma

Revertant mosaicism refers to a condition in which a pathogenic germline mutation is spontaneously corrected in somatic cells, resulting in the presence of two or more cell populations with different genotypes in an organism arising from a single fertilized egg. If the revertant cells are clonally expanded due to a survival advantage over the surrounding mutant cells, patients benefit from this self-healing phenomenon which leads to the development of milder-than-expected clinical phenotypes; in genetic skin diseases, patients with revertant mosaicism present with small islands of healthy skin. To date, revertant mosaicism has been reported in ∼50 genetic diseases involving the skin, blood, liver, muscle, and brain. In this review, I briefly summarize current knowledge on revertant mosaicism in two particular skin diseases, ichthyosis with confetti (IWC) and loricrin keratoderma (LK), both of which develop numerous revertant skin patches. Notably, homologous recombination (HR) is the only mechanism underlying the reversion of pathogenic mutations in IWC and LK, and this was identified following the analysis of ∼50 revertant epidermis samples. All the samples showed long-tract loss of heterozygosity (LOH) that originated at regions centromeric to pathogenic mutations and extended to the telomere of the mutation-harboring chromosomes. Elucidating the molecular mechanisms underlying revertant mosaicism in IWC and LK-especially how mutant proteins induce long-tract LOH-would potentially expand the possibility of manipulating HR to induce the reversion of disease-causing mutations and help devising novel therapies not only for IWC and LK but also for other intractable genetic diseases.

Somatic mosaicism of sex chromosomes in the blood and brain

In the blood, mosaic somatic aneuploidy (mSA) of all chromosomes has been found to be associated with adverse health outcomes, including hematological cancer. Sex chromosome mSA in the blood has been found to occur at a higher rate than autosomal mSA. Mosaic loss of the Y chromosome is the most common copy number alteration in males, and has been found to be associated with Alzheimer's disease (AD) in blood lymphocytes. mSA of the sex chromosomes has also been identified in the brain; however, little is known about its frequency across individuals. Using WGS data from 362 males and 719 females from the ROSMAP cohort, we quantified the relative rate of sex chromosome mSA in the dorsolateral prefrontal cortex (DLPFC), cerebellum and whole blood. To ascertain the functionality of observed sex chromosome mosaicism in the DLPFC, we examined its correlation with chromosome X and Y gene expression as well as neuropathological and clinical characteristics of AD and cognitive ageing. In males, we found that mSA of the Y chromosome occurs more frequently in blood than in the DLPFC or cerebellum. In the DLPFC, the presence of at least one APOE4 allele was associated with a reduction in read depth of the Y chromosome (p = 1.9e-02). In the female DLPFC, a reduction in chromosome X read depth was associated with reduced cognition at the last clinical visit and faster rate of cognitive decline (p = 7.8e-03; p = 1.9e-02). mSA of all sex chromosomes in the DLPFC were associated with aggregate measures of gene expression, implying functional impact. Our results provide insight into the relative rate of mSA between tissues and suggest that Y and female X chromosome read depth in the DLPFC is modestly associated with late AD risk factors and cognitive pathologies.

Novel Splice-Site Mutation of KRT1 Underlies Diffuse Palmoplantar Keratoderma in a Large Chinese Pedigree

AIMS

To identify potential causative gene mutations in a large Han Chinese pedigree with diffuse nonepidermolytic palmoplantar keratoderma (NEPPK).

METHODS

We enrolled 11 patients and 8 healthy individuals from a pedigree with NEPPK and 100 randomly selected healthy controls. Biopsy samples were obtained from the proband. Genomic DNA was extracted from a peripheral blood sample from each participant. Mutation detection via polymerase chain reaction and Sanger sequencing of relevant potential causative genes, including KRT1, KRT6C, KRT10, KRT16, AQP5, and SERPINB7, was performed. Comparisons were made between sequencing outcomes and currently available reference genome databases, including HGMD Pro, Pubmed, 1000 Genomics, and dbSNP.

RESULTS

Histological findings, clinical features, and medical history were in accordance with the diagnosis of diffuse NEPPK. We identified a novel splice-site mutation c.1255-1G > C in intron 6 of KRT1 in all individuals with NEPPK in the pedigree.

CONCLUSIONS

Diffuse NEPPK is a relatively rare subtype of palmoplantar keratoderma. The results of this study expand the spectrum of KRT1 mutations in diffuse NEPPK and provide insights into the understanding of its underlying pathological mechanisms and phenotype-genotype correlations.

Hemihyperplasia: History of medicine assists medical genetics

This paper examines the role of the history of medicine in case of congenital isolated hemihyperplasia. Isolated hemihyperplasia is a genetic disorder in which one side of the body grows more than the other, causing visible lateral asymmetry of the human body. The date of the occurrence of the genetic mutation that leads to hemihyperplasia is not known yet. The aim of the current research was to confirm or to disprove the fact that isolated hemihyperplasia was first described in the first half of the 19th century. Using the case of hemihyperplasia we aimed to demonstrate how historical analysis may assist medical genetics in cases when estimating a mutation date is necessary. Medical literature from 1573 onwards was searched for any mention of hemihypertrophy, hemihyperplasia, hemi-gigantism, partial gigantism, hemi-macrosomia and other possible descriptions for pathological lateral body overgrowth. Historical analysis suggests that the mutation in question occurred in the first half of the 19th century, approximately 200 years ago. This led to the appearance of hemihyperplasia and subsequent hemihyperplasia-including syndromes. An additional genetic research is needed for investigation of the development of the involved chromosomal region instability since this period. Such research may use the timeline orientation provided by the history of medicine.

Mosaicism in Cutaneous Disorders

Genetic mosaicism arises when a zygote harbors two or more distinct genotypes, typically due to de novo, somatic mutation during embryogenesis. The clinical manifestations largely depend on the differentiation status of the mutated cell; earlier mutations target pluripotent cells and generate more widespread disease affecting multiple organ systems. If gonadal tissue is spared-as in somatic genomic mosaicism-the mutation and its effects are limited to the proband, whereas mosaicism also affecting the gametes, such as germline or gonosomal mosaicism, is transmissible. Mosaicism is easily appreciated in cutaneous disorders, as phenotypically distinct mutant cells often give rise to lesions in patterns determined by the affected cell type. Genetic investigation of cutaneous mosaic disorders has identified pathways central to disease pathogenesis, revealing novel therapeutic targets. In this review, we discuss examples of cutaneous mosaicism, approaches to gene discovery in these disorders, and insights into molecular pathobiology that have potential for clinical translation.

Expanding the Mutation Spectrum of Ichthyosis with Confetti

Ichthyosis with confetti is a rare, autosomal dominant disorder caused by frameshift mutations in KRT10 or KRT1 and characterized by the development of white, genetically revertant macules in red, diseased skin. All cases result from mutations affecting the tail domains of keratin-10 or keratin-1, and Suzuki et al. expand the mutation spectrum for ichthyosis with confetti caused by mutations in KRT1, showing that a polyarginine frameshift in the keratin-1 tail can also cause this disorder.

Coexistence of mutations in keratin 10 (KRT10) and the mitochondrial genome in a patient with ichthyosis with confetti and Leber's hereditary optic neuropathy

Ichthyosis with confetti (IWC) is a severe congenital genodermatosis characterized by ichthyosiform erythroderma since birth and confetti-like spots of normal skin appearing in childhood as a results of revertant mosaicism. This disorder is caused by mutations in KRT10 or KRT1 genes. We report a 16-year-old boy who presented ichthyosiform erythroderma with severe desquamation since birth and gradually worsening psycho-neurological symptoms (mental retardation, ataxia, dystonia, hypoacusis). The patient conspicuously lacked typical confetti-like spots at the age of 16. The molecular diagnostics by the whole exome sequencing showed a novel de novo (c.1374-2A>C) mutation in the KRT10 gene responsible for the development of IWC (KRT10 defect was confirmed by immunofluorescent study). Concurrently, the m.14484T>C mutation in mitochondrial MTND6 gene (characteristic for Leber's hereditary optic neuropathy or LHON) was detected in patient, his mother and brother. LHON causes frequent inherited blindness typically appearing during young adult life whose expression can be triggered by additional factors such as smoking or alcohol exposure. We speculate the effects of KRT10 and LHON mutations influence each other-skin inflammatory reaction due to severe ichthyosis might trigger the development of psychoneurological abnormalities whereas the mitochondrial mutation may reduce revertant mosaicism phenomenon resulting in the lack of confetti-like spots characteristic for IWC. However, based on a single case we should be cautious about attributing phenotypes to digenic mechanisms without functional data.

Mutations in SULT2B1 Cause Autosomal-Recessive Congenital Ichthyosis in Humans

Ichthyoses are a clinically and genetically heterogeneous group of genodermatoses associated with abnormal scaling of the skin over the whole body. Mutations in nine genes are known to cause non-syndromic forms of autosomal-recessive congenital ichthyosis (ARCI). However, not all genetic causes for ARCI have been discovered to date. Using whole-exome sequencing (WES) and multigene panel screening, we identified 6 ARCI-affected individuals from three unrelated families with mutations in Sulfotransferase family 2B member 1 (SULT2B1), showing their causative association with ARCI. Cytosolic sulfotransferases form a large family of enzymes that are involved in the synthesis and metabolism of several steroids in humans. We identified four distinct mutations including missense, nonsense, and splice site mutations. We demonstrated the loss of SULT2B1 expression at RNA and protein levels in keratinocytes from individuals with ARCI by functional analyses. Furthermore, we succeeded in reconstructing the morphologic skin alterations in a 3D organotypic tissue culture model with SULT2B1-deficient keratinocytes and fibroblasts. By thin layer chromatography (TLC) of extracts from these organotypic cultures, we could show the absence of cholesterol sulfate, the metabolite of SULT2B1, and an increased level of cholesterol, indicating a disturbed cholesterol metabolism of the skin upon loss-of-function mutation in SULT2B1. In conclusion, our study reveals an essential role for SULT2B1 in the proper development of healthy human skin. Mutation in SULT2B1 leads to an ARCI phenotype via increased proliferation of human keratinocytes, thickening of epithelial layers, and altered epidermal cholesterol metabolism.

Revertant mosaicism in genodermatoses

Inherited monogenic skin disorders include blistering disorders, inflammatory disorders, and disorders of differentiation or development. In most cases, the skin is broadly involved throughout the affected individual's lifetime, but rarely, appearance of normal skin clones has been described. In these cases of revertant mosaicism, cells undergo spontaneous correction to ameliorate the effects of genetic mutation. While targeted reversion of genetic mutation would have tremendous therapeutic value, the mechanisms of reversion in the skin are poorly understood. In this review, we provide an overview of genodermatoses that demonstrate widespread reversion and their corrective mechanisms, as well as the current research aimed to understand this "natural gene therapy".