Ichthyosis: clinical manifestations and practical treatment options

Superior COL7A1 and TGM1 gene expression in difficult-to-transfect skin cell mediated by highly branched poly(β-amino esters) through stepwise fractionation

Delivering functional gene into targeted skin cells or tissues to modulate the genes expression, has the potential to treat various hereditary cutaneous disorders. Nevertheless, the lack of safe and effective gene delivery vehicles greatly limits the clinical translation of gene therapy for inherited skin diseases. Herein, we developed a facile elution fractionation strategy to isolate eight HPAEs with Mw ranging from 7.6 to 131.8 kg/mol and Đ < 2.0 from the one crude HPAE23.7k, and investigated the expression efficiency for TGM1 and COL7A1 plasmids. Gene transfection results revealed that the intermediate MW HPAEs, HPAE20.6k, exhibited the highest gene transfection efficiency (46.4%) and the strongest mean fluorescence intensity (143,032 RLU), compared to other isolated components and the crude product. Importantly, best-performing isolated HPAE effectively delivered COL7A1 (15,974 bp) and TGM1 (7181 bp) plasmids, promoting the efficient expression of type VII collagen (C7) and transglutaminase-1 proteins in cutaneous cells. Our study establishes a straightforward step-by-step elution fractionation strategy for the development of HPAEs gene delivery vectors, expediting their clinical translation in inherited skin diseases.

Advances in the treatment of autosomal recessive congenital ichthyosis, a look towards the repositioning of drugs

Autosomal recessive congenital ichthyoses (ARCI) are a skin pathology due to genetic causes characterized by a variable degree of desquamation, accompanied by erythema. The degree of symptoms is variable, different altered genes are involved, and the symptoms drastically affect patients' quality of life. Topical treatments are a first-choice strategy due to their ease of application and cost; however, enteral administration of retinoids offers greater efficacy, although with certain limitations. Despite the treatment alternatives, ARCI will persist throughout life, disabling people. Therefore, the search for new treatments always remains necessary. Especially repositioning drugs could be a short-term alternative to new affordable treatments for patients. Taking advantage of extensive knowledge of known drugs or biologics could ensure more accessible and possibly lower-cost treatments. This review briefly and concisely addresses possible repositioning strategies with drugs and biologics for ichthyosis.

Ophthalmic findings in patients with autosomal recessive lamellar ichthyosis due to TGM1 mutations in an isolated population

PURPOSE

To describe the ocular clinical characteristics of a group of Mexican patients with lamellar ichthyosis (LI) arising from TGM1 pathogenic variants.

METHODS

Ophthalmological exploration, pedigree analysis and genetic screening were performed in patients with an established clinical diagnosis of lamellar ichthyosis from families located in a small community in the Southeast of Mexico.

RESULTS

Nine patients with LI in five families were identified. There were six affected females. All patients (9/9) demonstrated eye lid abnormalities with eight patients showing lid margin abnormalities. Madarosis was present in only three individuals and corneal scarring was documented in two. All nine individuals carried biallelic TGM1 variants, either homozygously or as compound heterozygous.

CONCLUSION

Ocular anomalies are common in individuals with TGM1-related LI. The occurrence of a variety of private or rare mutations hampers the identification of a genotype-phenotype correlation for ocular anomalies in this disorder.

Netherton syndrome in a Bulgarian patient : Presentation of a case and an update of therapeutic options

Comel-Netherton syndrome, or Netherton syndrome (NS), is a rare chronic genetic skin condition affecting the daily life of patients, which often results in poorly developed social skills and anxiety. Genetic predisposition plays a key role alongside the clinical findings, and clinicians must be aware of it as it can mimic other well-known skin conditions. Diagnosis is challenging both clinically and histologically. Clinically, it can mimic a severe form of atopic dermatitis, psoriasiform dermatitis overlapping with atopic dermatitis, or erythrokeratodermia variabilis. The difficulties in making histological diagnosis are similar, and it is often necessary to take several biopsies in order to clarify the diagnosis. Although retinoids are used for both psoriasis, erythrokeratodermia variabilis, and other congenital forms of keratodermia, the recommended treatment doses are different. This often results in poor treatment outcome. We present a 16-year-old patient previously diagnosed as erythrokeratodermia variabilis and treated with little to no improvement. Systemic therapy with acitretin 10 mg daily, local pimecrolimus 1%, emollients, and bilastine 20 mg once daily was initiated. Due to the limited application of retinoids and the difficulties in achieving permanent remission, modern medicine is faced with the challenge of seeking innovative therapeutic solutions. New hopes are placed on targeted or anti-cytokine therapy, based on inhibiting the inflammatory component of the disease. This article is mainly focused on innovative therapeutic options, including modern medications such as dupilumab, infliximab, secukinumab, anakinra, omalizumab, and others.

Ichthyosis: presentation and management

PURPOSE OF REVIEW

This review focuses on the presentation and management of ichthyoses and highlights recent advances in treatment that hold promise for better targeted therapy.

RECENT FINDINGS

The ichthyoses are a group of rare genetic diseases with a wide phenotypic spectrum, characterized most often by generalized hyperkeratosis and scaling with variable erythema. The highly visible scaling and frequent itch contribute to decreased quality of life. Management for ichthyosis focuses on symptomatic relief and scale reduction with emollients, keratolytics, and retinoids. Recent advances in immune profiling and genotype-phenotype mapping have increased understanding of ichthyosis and shifted focus to pathogenesis-based targeted therapies with emerging biologics, small molecular inhibitors, and gene therapy.

SUMMARY

This article discusses clinical assessment and genotyping to make the diagnosis of specific forms of ichthyosis, provides guidance for management, and reviews new treatment options with systemic agents.

Identification of carrier status of Xp22.31 microdeletions associated with X-linked ichthyosis at the single-cell level using haplotype linkage analysis by karyomapping

PURPOSE

Currently, owing to the limitations of high-throughput sequencing depth and the allele dropout caused by the whole-genome amplification, detection of chromosomal variants in embryos with CNVs <5 Mb is unsatisfactory at the single-cell level using only conventional sequencing methods. Therefore, here we aimed to use a strategy of preimplantation genetic testing for monogenic (PGT-M) to compensate for the shortcomings of conventional sequencing methods. The purpose of this study is to report the effectiveness of haplotype linkage analysis by karyomapping for preimplantation diagnosis microdeletion diseases.

METHODS

Six couples carrying chromosomal microdeletions associated with X-linked ichthyosis were recruited, and all couples entered the PGT process. Multiple displacement amplification (MDA) method was used to amplify the whole-genome DNA of trophectoderm cells. Then karyomapping based on single nucleotide polymorphism (SNP) was used for haplotype linkage analysis to detect alleles carrying microdeletions, and CNVs of embryos were identified to determine euploid identity. Amniotic fluid tests were performed in the second trimester to verify the PGT-M results.

RESULTS

All couples were tested for chromosomal microdeletions, with deletion fragments ranging in size from 1.60 to 1.73 Mb, and one partner in each couple did not carry the microdeletion. Three couples successfully underwent PGT-M assisted conception and obtained healthy live births.

CONCLUSION

This study shows that haplotype linkage analysis by karyomapping could effectively detect the carrier status of embryos with microdeletions at the single-cell level. This approach may be applied to the preimplantation diagnosis of various chromosomal microvariation diseases.

Congenital ichthyosis: a multidisciplinary approach in a neonatal care unit

Congenital ichthyoses are a rare group of genetic disorders caused by defects in the two outermost skin layers, resulting in an abnormal barrier function. We report the case of a male preterm neonate presenting at delivery with thickened and scaling skin, ectropium and eclabium. Supportive care aiming at improving skin condition and handling possible complications was provided. Following gradual clinical improvement, he was discharged after 27 days. Molecular testing identified mutations in a gene encoding lipoxygenase (ALOX12B), associated with autosomal recessive congenital ichthyosis. This case highlights an uncommon disease that can determine significant morbidity and mortality in the first few weeks of life. Management of this complex disease benefits from a multidisciplinary approach. Molecular studies allow a more accurate diagnosis and enable genetic counselling.

Ichthyosis

The ichthyoses are a large, heterogeneous group of skin cornification disorders. They can be inherited or acquired, and result in defective keratinocyte differentiation and abnormal epidermal barrier formation. The resultant skin barrier dysfunction leads to increased transepidermal water loss and inflammation. Disordered cornification is clinically characterized by skin scaling with various degrees of thickening, desquamation (peeling) and erythema (redness). Regardless of the type of ichthyosis, many patients suffer from itching, recurrent infections, sweating impairment (hypohidrosis) with heat intolerance, and diverse ocular, hearing and nutritional complications that should be monitored periodically. The characteristic clinical features are considered to be a homeostatic attempt to repair the skin barrier, but heterogeneous clinical presentation and imperfect phenotype-genotype correlation hinder diagnosis. An accurate molecular diagnosis is, however, crucial for predicting prognosis and providing appropriate genetic counselling. Most ichthyoses severely affect patient quality of life and, in severe forms, may cause considerable disability and even death. So far, treatment provides only symptomatic relief. It is lifelong, expensive, time-consuming, and often provides disappointing results. A better understanding of the molecular mechanisms that underlie these conditions is essential for designing pathogenesis-driven and patient-tailored innovative therapeutic solutions.

Identification and In Silico Analysis of a Homozygous Nonsense Variant in TGM1 Gene Segregating with Congenital Ichthyosis in a Consanguineous Family

Background and Objectives: Lamellar ichthyosis is a rare skin disease characterized by large, dark brown plate-like scales on the entire body surface with minimum or no erythema. This phenotype is frequently associated with a mutation in the TGM1 gene, encoding the enzyme transglutaminase 1 which plays a catalytic role in the formation of the cornified cell envelop. The present study aimed to carry out clinical and genetic characterization of the autosomal recessive lamellar ichthyosis family from Balochistan. Materials and Methods: A consanguineous family with lamellar ichthyosis was enrolled from Balochistan, Pakistan. PCR amplification of all the exons and splice site junctions of the TGM1 gene followed by Sanger sequencing was performed on the genomic DNA. The identified variant was checked by In silico prediction tools to evaluate the effect of the variant on protein. Results: Sanger sequencing identified a homozygous nonsense variant c.131G >A (p.Trp44*) in the TGM1 gene that segregated in the autosomal recessive mode of inheritance in the family. The identified variant results in premature termination of transcribed mRNA and is predicted to cause a truncated or absent translation product transglutaminase-1 (TGase-1) accompanied by loss of catalytic activity, causing a severe clinical phenotype of lamellar ichthyosis in the patients. Conclusions: Here, we report a consanguineous lamellar ichthyosis family with a homozygous nonsense variant in the TGM1 gene. The variant is predicted as pathogenic by different In silico prediction tools.

Dual antibody inhibition of KLK5 and KLK7 for Netherton syndrome and atopic dermatitis

The epidermis is a barrier that prevents water loss while keeping harmful substances from penetrating the host. The impermeable cornified layer of the stratum corneum is maintained by balancing continuous turnover driven by epidermal basal cell proliferation, suprabasal cell differentiation, and corneal shedding. The epidermal desquamation process is tightly regulated by balance of the activities of serine proteases of the Kallikrein-related peptidases (KLK) family and their cognate inhibitor lymphoepithelial Kazal type-related inhibitor (LEKTI), which is encoded by the serine peptidase inhibitor Kazal type 5 gene. Imbalance of proteolytic activity caused by a deficiency of LEKTI leads to excessive desquamation due to increased activities of KLK5, KLK7, and KLK14 and results in Netherton syndrome (NS), a debilitating condition with an unmet clinical need. Increased activity of KLKs may also be pathological in other dermatoses such as atopic dermatitis (AD). Here, we describe the discovery of inhibitory antibodies against murine KLK5 and KLK7 that could compensate for the deficiency of LEKTI in NS. These antibodies are protective in mouse models of NS and AD and, when combined, promote improved skin barrier integrity and reduced inflammation. To translate these findings, we engineered a humanized bispecific antibody capable of potent inhibition of human KLK5 and KLK7. A crystal structure of KLK5 bound to the inhibitory Fab revealed that the antibody binds distal to its active site and uses a relatively unappreciated allosteric inhibition mechanism. Treatment with the bispecific anti-KLK5/7 antibody represents a promising therapy for clinical development in NS and other inflammatory dermatoses.

Transcriptomic Analysis of the Major Orphan Ichthyosis Subtypes Reveals Shared Immune and Barrier Signatures

Preliminary work suggested upregulation of inflammatory pathways in patients with common forms of ichthyosis. However, a comprehensive characterization of skin from various ichthyosis subtypes is unavailable, precluding the development of targeted treatments. Thus, we sought to characterize the immune and barrier profiles of common and subtype-specific skin transcriptomes in a large group of patients with ichthyosis. We performed a global RNA-sequencing analysis in 54 patients with ichthyosis (7 with Netherton syndrome, 13 with epidermolytic ichthyosis, 16 with lamellar ichthyosis, and 18 with congenital ichthyosiform erythroderma) and 40 healthy controls. Differentially expressed genes were defined on the basis of fold changes > 2 and false discovery rate < 0.05 criteria. We found robust and significant T helper (Th) 22/Th17 skewing in all subtypes (e.g., IL-17A/C/F, S100A7/8/9/12; P < 0.001) with modest changes in Th2 pathway, primarily in Netherton syndrome, and Th1 skewing in congenital ichthyosiform erythroderma. Across all subtypes (less evident in epidermolytic ichthyosis), lipid metabolism and barrier junction markers were downregulated (e.g., FA2H, CDH10/11/12/2; P < 0.05), whereas epidermal cornification and proliferation measures were upregulated (e.g., SPRR1A/1B/2C/2G, EREG; P < 0.05). Our findings suggest that the common ichthyosis variants share aberrations in Th17/Th22 and barrier function, with minimal Th2 modulation. This may help to elucidate the pathogeneses of these subtypes and inform the development of subtype-specific treatments.

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.

Current Strategies for the Gene Therapy of Autosomal Recessive Congenital Ichthyosis and Other Types of Inherited Ichthyosis

Mutations in genes such as transglutaminase-1 (TGM1), which are responsible for the formation and normal functioning of a lipid barrier, lead to the development of autosomal recessive congenital ichthyosis (ARCI). ARCIs are characterized by varying degrees of hyperkeratosis and the presence of scales on the body surface since birth. The quality of life of patients is often significantly affected, and in order to alleviate the manifestations of the disease, symptomatic therapy with moisturizers, keratolytics, retinoids and other cosmetic substances is often used to improve the condition of the patients' skin. Graft transplantation is commonly used to correct defects of the eye. However, these approaches offer symptomatic treatment that does not restore the lost protein function or provide a long-term skin barrier. Gene and cell therapies are evolving as promising therapy for ARCIs that can correct the functional activity of altered proteins. However, these approaches are still at an early stage of development. This review discusses current studies of gene and cell therapy approaches for various types of ichthyosis and their further prospects for patient treatment.

Bioengineered Efficacy Models of Skin Disease: Advances in the Last 10 Years

Models of skin diseases, such as psoriasis and scleroderma, must accurately recapitulate the complex microenvironment of human skin to provide an efficacious platform for investigation of skin diseases. Skin disease research has been shifting from less complex and less relevant 2D (two-dimensional) models to significantly more relevant 3D (three-dimensional) models. Three-dimensional modeling systems are better able to recapitulate the complex cell–cell and cell–matrix interactions that occur in vivo within skin. Three-dimensional human skin equivalents (HSEs) have emerged as an advantageous tool for the study of skin disease in vitro. These 3D HSEs can be highly complex, containing both epidermal and dermal compartments with integrated adnexal structures. The addition of adnexal structures to 3D HSEs has allowed researchers to gain more insight into the complex pathology of various hereditary and acquired skin diseases. One method of constructing 3D HSEs, 3D bioprinting, has emerged as a versatile and useful tool for generating highly complex HSEs. The development of commercially available 3D bioprinters has allowed researchers to create highly reproducible 3D HSEs with precise integration of multiple adnexal structures. While the field of bioengineered models for study of skin disease has made tremendous progress in the last decade, there are still significant efforts necessary to create truly biomimetic skin disease models. In future studies utilizing 3D HSEs, emphasis must be placed on integrating all adnexal structures relevant to the skin disease under investigation. Thorough investigation of the intricate pathology of skin diseases and the development of effective treatments requires use of highly efficacious models of skin diseases.

Variants in the PNPLA1 Gene in Families with Autosomal Recessive Congenital Ichthyosis Reveal Clinical Significance

The term autosomal recessive congenital ichthyosis (ARCI) is the subgroup of ichthyosis, which describes a highly heterogeneous group of genetic disorders of the skin characterized by cornification and defective keratinocytes differentiation associated with mutations in at least 14 genes including PNPLA1. To study the molecular basis of the Pakistani kindreds (A and B) affected by ARCI, whole-exome sequencing (WES) in the DNA samples of affected members was performed followed by Sanger sequencing of the candidate gene to hunt down the disease-causing sequence variant/s. WES data analysis led to the identification of a novel nonsense sequence variant (c.892C>T; p.Arg298*, family A) and a recurrent missense variant (c.102C>A; p.Asp34Glu, family B) in PNPLA1 mapped to the ARCI locus in chromosome 6p21.31. Validation and cosegregation analysis of the variants in the remaining family members of the respective families were confirmed by Sanger sequencing. The current investigation expands the spectrum of PNPLA1 mutations and helps establish the proper clinico-genetic diagnosis and correct genotype-phenotype correlation.

Clinical features and genetic analysis of two Chinese families with X-linked ichthyosis

Objective

Recessive X-linked ichthyosis (RXLI) caused by deficiency of the steroid sulfatase gene (STS) has a reported prevalence of 1/2000 to 1/6000. The present study aimed to characterize the phenotypes and genotypes of two Chinese families with RXLI.

Methods

The patients were referred to the Family Planning Research Institute of Hunan Province for genetic counseling. Their skin phenotypes were photographed, and venous blood was drawn and used for chromosomal microarray analysis (CMA).

Results

The skin phenotype of the proband from the first family was characterized by generalized skin dryness and scaling, with noticeable dark brown, polygonal scales on his trunk and extensor surfaces of his extremities. The proband from the second family had an atypical phenotype showing mild skin dryness over his entire body, slight scaling on his abdomen, and small skin fissures on his arms and legs. No mental disability or developmental anomaly was noted in either proband. CMA revealed that both probands carried a 1.4-Mb deletion on chromosome Xp22.31 involving four Online Mendelian Inheritance in Man-listed genes including STS.

Conclusions

Our findings add knowledge to the genotype and phenotype spectrum of RXLI, which may be helpful in genetic counseling and prenatal diagnosis.

Netherton Syndrome in Children: Management and Future Perspectives

Netherton syndrome (NS) is a genetic, multisystemic disease classically distinguished by a triad of clinical manifestations: congenital ichthyosiform erythroderma, hair shaft abnormalities, and immune dysregulation. Due to the complex pathogenesis of the disease, there are no specific therapies currently accessible for patients with NS. An early diagnosis is crucial to start the correct management of these patients. A multidisciplinary approach, including specialists in immunology, allergology, and dermatology, is necessary to set up the best therapeutic pathway. We conducted a review with the aim to summarize the different therapeutic strategies currently accessible and potentially available in the future for children with NS. However, given the limited data in the literature, the best-tailored management should be decided upon the basis of the specific clinical characteristics of the patients with this rare clinical condition. Further comprehension of the pathophysiology of the disease could lead to more efficacious specific therapeutic options, which could allow a change in the natural history of NS.

Molecular epidemiology of non-syndromic autosomal recessive congenital ichthyosis in a Middle-Eastern population

Autosomal recessive congenital ichthyosis (ARCI) is a rare and heterogeneous skin cornification disorder presenting with generalized scaling and varying degrees of erythema. Clinical manifestations range from lamellar ichthyosis (LI), congenital ichthyosiform erythroderma (CIE) through the most severe form of ARCI, Harlequin ichthyosis (HI). We used homozygosity mapping, whole-exome and direct sequencing to delineate the relative distribution of pathogenic variants as well as identify genotype-phenotype correlations in a cohort of 62 Middle Eastern families with ARCI of various ethnic backgrounds. Pathogenic variants were identified in most ARCI-associated genes including TGM1 (21%), CYP4F22 (18%), ALOX12B (14%), ABCA12 (10%), ALOXE3 (6%), NIPAL4 (5%), PNPLA1 (3%), LIPN (2%) and SDR9C7 (2%). In 19% of cases, no mutation was identified. Our cohort revealed a higher prevalence of CYP4F22 and ABCA12 pathogenic variants and a lower prevalence of TGM1 and NIPAL4 variants, as compared to data obtained in other regions of the world. Most variants (89%) in ALOX12B were associated with CIE and were the most common cause of ARCI among patients of Muslim origin (26%). Palmoplantar keratoderma associated with fissures was exclusively a result of pathogenic variants in TGM1. To our knowledge, this is the largest cohort study of ARCI in the Middle-Eastern population reported to date. Our data demonstrate the importance of population-tailored mutation screening strategies and shed light upon specific genotype-phenotype correlations.

Novel Homozygous Mutations in the Genes TGM1, SULT2B1, SPINK5 and FLG in Four Families Underlying Congenital Ichthyosis

Background: Ichthyoses are a large group of hereditary cornification disorders, which are both clinically and etiologically heterogeneous and affect mostly all the skin surface of the patients. Ichthyosis has its origin in an ancient Greek word “ichthys” meaning fish, this is because the ichthyosis patients have dry, thickened, and scaly skin. There is an excess accumulation of epidermal cells resulting in the appearance of continuous and widespread scales on the body. There are many varieties of ichthyosis with a broad spectrum of intensity, severity, and associated symptoms, most of them are extremely rare. Ichthyosis vulgaris is the most frequently occurring type of ichthyoses. Method: The present study consists of four Pakistani ichthyosis families (A, B, C, and D). Whole exome sequencing (WES) approach was used to identify the pathogenic sequence variants in probands. The segregation of these variants in other participants was confirmed by Sanger sequencing. Results: Total four variants including, two splice site (TGM1: c.2088 + 1G > A) and (SPINK5: c.882 + 1G > T), a missense (SULT2B1: c.419C > T; p. Ala140Val), and a nonsense (FLG: c.6109C > T; p. Arg2037Ter) variant were identified in families A, C, B, and D, respectively, as causative mutations responsible for ichthyosis in these families. Conclusion: Our study unravels the molecular etiology of the four Pakistani ichthyosis families and validates the involvement of TGM1, SULT2B1, SPINK5, and FLG, in the etiology of different forms of ichthyosis. In addition, this study also aims to give a detailed clinical report of the studied ichthyosis families.

3D model of harlequin ichthyosis reveals inflammatory therapeutic targets

The biology of harlequin ichthyosis (HI), a devastating skin disorder caused by loss-of-function mutations in the gene ABCA12, is poorly understood, and to date, no satisfactory treatment has been developed. We sought to investigate pathomechanisms of HI that could lead to the identification of new treatments for improving patients' quality of life. In this study, RNA-Seq and functional assays were performed to define the effects of loss of ABCA12 using HI patient skin samples and an engineered CRISPR/Cas9 ABCA12 KO cell line. The HI living skin equivalent (3D model) recapitulated the HI skin phenotype. The cytokines IL-36α and IL-36γ were upregulated in HI skin, whereas the innate immune inhibitor IL-37 was strongly downregulated. We also identified STAT1 and its downstream target inducible nitric oxide synthase (NOS2) as being upregulated in the in vitro HI 3D model and HI patient skin samples. Inhibition of NOS2 using the inhibitor 1400W or the JAK inhibitor tofacitinib dramatically improved the in vitro HI phenotype by restoring the lipid barrier in the HI 3D model. Our study has identified dysregulated pathways in HI skin that are feasible therapeutic targets.

Prenatal diagnosis of harlequin ichthyosis by ultrasonography: a case report

Autosomal recessive congenital ichthyosis is a genetically and phenotypically heterogeneous group of skin disorders, including harlequin ichthyosis (HI), lamellar ichthyosis, and bullous congenital ichthyosiform erythroderma. HI is the most phenotypically severe autosomal recessive congenital ichthyosis associated with the mutation of the adenosine triphosphate—binding cassette subfamily A member 12 (ABCA12) gene. The clinical manifestations include generalized hyperkeratotic plaques and deep fissures, ectropion, eclabium, and contractures. However, the severe HI may easily be misdiagnosed as epidermolysis bullosa or syndromic ichthyosis. Meanwhile, no consensus exists about the best used in clinical trials or clinical practice when more elaborate scoring systems have been proposed to evaluate skin xerosis, palmoplantar keratoderma, and disease extension an accurate prenatal diagnosis is necessary. Until the ABCA12 gene was identified as the pathogenic gene, prenatal diagnosis of HI had been performed by the invasive techniques of fetal skin biopsy. Now, advances in ultrasound technology and fetal DNA-based analysis have replaced it. The mortality rate is markedly high and prompt; prenatal diagnosis of neonate HI is critical for appropriate perinatal and postnatal management. It is also essential to prepare parents for future pregnancies and reduce the family’s physical and mental distress and financial burden. This report presents a rare case of harlequin ichthyosis diagnosed by the ultrasound and discusses the significance of prenatal ultrasound diagnosis and molecular diagnosis in the prenatal diagnosis of HI.

Topical Aminosalicylic Acid Improves Keratinocyte Differentiation in an Inducible Mouse Model of Harlequin Ichthyosis

Mutations in the lipid transport protein ABCA12 cause the life-threatening skin condition harlequin ichthyosis (HI), which is characterized by the loss of skin barrier function, inflammation, and dehydration. Inflammatory responses in HI increase disease severity by impairing keratinocyte differentiation, suggesting amelioration of this phenotype as a possible therapy for the condition. Existing treatments for HI are based around the use of retinoids, but their value in treating patients during the neonatal period has been questioned relative to other improved management regimens, and their long-term use is associated with side effects. We have developed a conditional mouse model to demonstrate that topical application of the aminosalicylic acid derivatives 5ASA or 4ASA considerably improves HI keratinocyte differentiation without the undesirable side effects of the retinoid acitretin and salicylic acid (aspirin). Analysis of changes in gene expression shows that 4ASA in particular elicits compensatory upregulation of a large family of barrier function-related genes, many of which are associated with other ichthyoses, identifying this compound as a lead candidate for developing topical treatments for HI.

Inflammation impairs keratinocyte differentiation and worsens harlequin ichthyosis

Harlequin ichthyosis mice can be used to assess therapies for this disease

Aminosalicylic acids may be therapeutic treatments for harlequin ichthyosis

4ASA improves skin differentiation and barrier function in harlequin ichthyosis models

Feasibility of a Wearable Reflectometric System for Sensing Skin Hydration

One of the major goals of Health 4.0 is to offer personalized care to patients, also through real-time, remote monitoring of their biomedical parameters. In this regard, wearable monitoring systems are crucial to deliver continuous appropriate care. For some biomedical parameters, there are a number of well established systems that offer adequate solutions for real-time, continuous patient monitoring. On the other hand, monitoring skin hydration still remains a challenging task. The continuous monitoring of this physiological parameter is extremely important in several contexts, for example for athletes, sick people, workers in hostile environments or for the elderly. State-of-the-art systems, however, exhibit some limitations, especially related with the possibility of continuous, real-time monitoring. Starting from these considerations, in this work, the feasibility of an innovative time-domain reflectometry (TDR)-based wearable, skin hydration sensing system for real-time, continuous monitoring of skin hydration level was investigated. The applicability of the proposed system was demonstrated, first, through experimental tests on reference substances, then, directly on human skin. The obtained results demonstrate the TDR technique and the proposed system holds unexplored potential for the aforementioned purposes.

Cushing disease in a patient with nonbullous congenital ichthyosiform erythroderma: lessons in avoiding glucocorticoids in ichthyosis

Nonbullous congenital ichthyosis erythroderma (CIE) is an autosomal recessive disorder of ineffective keratinization. We present a unique case of a 16-year-old female with CIE who developed Cushing disease (CD) at age 13 with concomitant worsening of her skin disease. After transsphenoidal resection of her pituitary adenoma, she had both resolution of her Cushing symptoms and significantly milder skin manifestations of her CIE. To the best of our knowledge, this is the first reported case of a patient with both CD and CIE, one that is important in demonstrating the role of glucocorticoids in this disorder.

Infant skin care: updates and recommendations

PURPOSE OF REVIEW

Neonatal skin acclimates rapidly to dry, aerobic conditions at birth and skin function gradually matures throughout infancy. Gentle skin care practices support the ongoing development and function of newborn skin. This article reviews research updates and current skin care recommendations for full-term infants, premature infants, and infants born with severe cutaneous manifestations of genetic skin disorders.

RECENT FINDINGS

Although safe early bathing of full-term infants with environmental controls is possible, delaying the first newborn bath for 12-24 h of life offers benefits of increased parental bonding and breastfeeding success. Swaddled bathing every 4 days is an effective bathing strategy for premature neonates. Among infants with a family history of atopic dermatitis, regular application of bland skin moisturizers reduces their risk of developing the disease. For newborns with erosive or blistering genetic skin conditions, use of specialized wound dressings and emollients promotes wound healing and helps limit skin damage. Environmental control with humidified incubators helps prevent life-threatening hypernatremic dehydration among babies born with collodion membranes; however, affected infants can tolerate breaks outside of the humidifier to promote parent-infant bonding.

SUMMARY

This article reviews infant skin care recommendations relevant to pediatric practice. Research to further optimize newborn skin care is ongoing, particularly, for the special populations of premature neonates and infants born with severe skin disease.

Management of congenital ichthyoses: European guidelines of care, part one

These guidelines for the management of congenital ichthyoses have been developed by a multidisciplinary group of European experts following a systematic review of the current literature, an expert conference held in Toulouse in 2016 and a consensus on the discussions. They summarize evidence and expert-based recommendations and are intended to help clinicians with the management of these rare and often complex diseases. These guidelines comprise two sections. This is part one, covering topical therapies, systemic therapies, psychosocial management, communicating the diagnosis and genetic counselling.

Management of congenital ichthyoses: European guidelines of care, part two

These guidelines for the management of congenital ichthyoses have been developed by a multidisciplinary group of European experts following a systematic review of the current literature, an expert conference held in Toulouse in 2016, and a consensus on the discussions. These guidelines summarize evidence and expert-based recommendations and intend to help clinicians with the management of these rare and often complex diseases. These guidelines comprise two sections. This is part two, covering the management of complications and the particularities of some forms of congenital ichthyosis.

Cross-sectional survey on disease severity in Japanese patients with harlequin ichthyosis/ichthyosis: Syndromic forms and quality-of-life analysis in a subgroup

BACKGROUND

Congenital ichthyoses (CIs) adversely affect quality of life (QOL) in patients. However, the effects of CIs on patient QOL have not been studied sufficiently.

OBJECTIVE

To investigate the association between disease severity and QOL in patients with harlequin ichthyosis (HI) and ichthyosis: syndromic forms (ISFs) METHODS: Clinical information of patients with HI and ISFs from 2010 to 2015 were obtained from 100 dermatology departments/divisions of principal institutes/hospitals throughout Japan. We examined the relationship between disease severity and QOL in patients with HI and ISFs. Patients who were aged 8 years or older and participated in a multicenter retrospective questionnaire survey in Japan were assessed by dermatology life quality index (DLQI, range of 0-30) and clinical ichthyosis score (range of 0-100).

RESULTS

Netherton syndrome patients had a significantly higher risk of allergy to food or environmental allergens than patients with other phenotypes. Keratitis-ichthyosis-deafness (KID) syndrome patients showed a significantly higher risk of skin infections than patients with other phenotypes. Complete data on DLQI were obtained from 13 patients, whose median age was 21 (8-71) years. Nine patients were male, and 4 were female. Systemic retinoids were administrated to 2 of the 3 HI patients. The Spearman's correlation coefficient between the clinical ichthyosis score and DLQI was 0.611 (P < 0.05).

CONCLUSION

We confirmed that Netherton syndrome and KID syndrome patients have a higher risk of allergy to food or environmental allergens and of skin infections, respectively. QOL impairment correlates with disease severity in HI and ISFs patients.

Collodion baby case series: the success of oral retinoic acid

Ichthyosis is a clinical skin cornification disorder characterized by hyperkeratosis. Lamellar ichthyosis is a rare form of ichthyosis (collodion baby), which is autosomal recessive. Diagnostic clinical findings can be confirmed with skin biopsy and genetic analysis. The principles of treatment are moistening the skin, prevention of dehydration, and use of keratolytic agents. Systemic retinoic acid (0.5-1 mg/kg/day) is reported to provide dramatic benefits in the treatment of lamellar ichthyosis and congenital ichthyosiform erythroderma. In this study, the efficiency of oral retinoic acid treatment is presented to show a dramatic improvement in five patients who were diagnosed as collodion babies and admitted to The Neonatal Intensive Care Unit after birth. None had other congenital problems. Only two patients were diagnosed as having sepsis. Hair loss was the only adverse effect of treatment in all five patients. With this series of collodion baby, we wanted to the draw the attention of physicians to the promising efficacy of retinoic acid.

Eyelash length for the diagnosis of atopic dermatitis and ichthyosis vulgaris in children-a case control study

Eyelash trichomegaly (ET) is increased length (≥ 12 mm), curling, pigmentation, or thickness of eyelashes. Among acquired causes, allergic diseases and atopic dermatitis (AD) have been found to be associated with eyelash trichomegaly especially in children; however, to date, this claim has not been studied in detail. To compare the eyelash lengths of AD and ichthyosis vulgaris (IV) patients with those of age- and sex-matched patients with unrelated skin disorders, we measured (with a digital Vernier caliper) and compared the eyelash lengths of AD (n = 58) and IV (n = 31) patients to those of age- and sex-matched patients with unrelated skin disorders (n = 178). The eyelashes of the AD and male IV patients were found to be significantly longer than those of the controls (p < 0.05). The severity of atopic dermatitis, i.e., SCORAD of > 50, hyperlinearity of palms and soles, and high IgE levels significantly correlated with the long eyelashes. The limitations of study are single-center study and filaggrin gene mutation in patients of IV could not be studied.

CONCLUSION

Thus, long eyelashes may act as surrogate marker of severe AD and serve as a cutaneous marker of IV patients. What is Known: • Among acquired causes, allergic diseases and atopic dermatitis have been found to be associated with eyelash trichomegaly especially in children. What is New: • The severity of atopic dermatitis, i.e., SCORAD of > 50, hyperlinearity of palms and soles, and high IgE levels significantly correlate with the long eyelashes; thus, long eyelashes may act as surrogate marker of severe atopic dermatitis. • It may also serve as a cutaneous marker of ichthyosis vulgaris especially in male patients and patients with palmoplantar hyperlinearity.

Ichthyosis molecular fingerprinting shows profound TH17 skewing and a unique barrier genomic signature

BACKGROUND

Ichthyoses are a group of rare skin disorders lacking effective treatments. Although genetic mutations are progressively delineated, comprehensive molecular phenotyping of ichthyotic skin could suggest much-needed pathogenesis-based therapy.

OBJECTIVE

We sought to profile the molecular fingerprint of the most common orphan ichthyoses.

METHODS

Gene, protein, and serum studies were performed on skin and blood samples from 29 patients (congenital ichthyosiform erythroderma, n = 9; lamellar ichthyosis, n = 8; epidermolytic ichthyosis, n = 8; and Netherton syndrome, n = 4), as well as age-matched healthy control subjects (n = 14), patients with psoriasis (n = 30), and patients with atopic dermatitis (AD; n = 16).

RESULTS

Using criteria of a fold change of greater than 2 and a false discovery rate of less than 0.05, 132 differentially expressed genes were shared commonly among all ichthyoses, including many IL-17 and TNF-α-coregulated genes, which are considered hallmarks of psoriasis (defensin beta 4A, kynureninase, and vanin 3). Although striking upregulation of TH17 pathway genes (IL17F and IL36B/G) resembling that seen in patients with psoriasis was common to all patients with ichthyoses in a severity-related manner, patients with Netherton syndrome showed the greatest T-cell activation (inducible costimulator [ICOS]) and a broader immune phenotype with T_H1/IFN-γ, OASL, and T_H2/IL-4 receptor/IL-5 skewing, although less than seen in patients with AD (all P < .05). Ichthyoses lacked the epidermal differentiation and tight junction alterations of patients with AD (loricrin, filaggrin, and claudin 1) but showed characteristic alterations in lipid metabolism genes (ELOVL fatty acid elongase 3 and galanin), with parallel reductions in extracellular lipids and corneocyte compaction in all ichthyoses except epidermolytic ichthyosis, suggesting phenotypic variations. Transepidermal water loss, a functional barrier measure, significantly correlated with IL-17-regulated gene expression (IL17F and IL36A/IL36B/IL36G).

CONCLUSION

Similar to patients with AD and psoriasis, in whom cytokine dysregulation and barrier impairment orchestrate disease phenotypes, psoriasis-like immune dysregulation and lipid alterations characterize the ichthyoses. These data support the testing of IL-17/IL-36-targeted therapeutics for patients with ichthyosis similar to those used in patients with psoriasis.

Surgical management of digital ischemia caused by constriction band formation in a patient with ichthyosis vulgaris

Ichthyosis is a broad and loosely defined group of hereditary and acquired disorders characterized by filaggrin dysfunction and impaired epidermal homeostasis that results in dry, scaly and thickened skin. Individuals with truncation mutations in the profilaggrin gene coding for filaggrin are strongly predisposed to severe forms of ichthyosis. The phenotypical expression of ichthyosis caused by the same genotypical mutation can vary considerably in severity and in regards to how much constricting scar tissue develops. Here, we report a case of digital ichthyosis threatening the neurovascular integrity to the small finger to discuss the importance of early diagnosis and role of Z-plasty flaps in the surgical treatment of constriction band formation.

Inherited Nonsyndromic Ichthyoses: An Update on Pathophysiology, Diagnosis and Treatment

Hereditary ichthyoses are due to mutations on one or both alleles of more than 30 different genes, mainly expressed in the upper epidermis. Syndromic as well as nonsyndromic forms of ichthyosis exist. Irrespective of etiology, virtually all types of ichthyosis exhibit a defective epidermal barrier that constitutes the driving force for hyperkeratosis, skin scaling, and inflammation. In nonsyndromic forms, these features are most evident in severe autosomal recessive congenital ichthyosis (ARCI) and epidermolytic ichthyosis, but to some extent also occur in the common type of non-congenital ichthyosis. A correct diagnosis of ichthyosis-essential not only for genetic counseling but also for adequate patient information about prognosis and therapeutic options-is becoming increasingly feasible thanks to recent progress in genetic knowledge and DNA sequencing methods. This paper reviews the most important aspects of nonsyndromic ichthyoses, focusing on new knowledge about the pathophysiology of the disorders, which will hopefully lead to novel ideas about therapy.

Ocular manifestations, complications and management of congenital ichthyoses: a new look

Congenital ichthyoses (CI) are rare genetic skin keratinisation diseases characterised by generalised scaling and a variable degree of erythema and hyperkeratosis. Ocular involvement includes the eyelids, conjunctiva and all layers of the cornea. Ophthalmic input should include regular slit lamp review with the primary aim to prevent a corneal epithelial defect, secondary bacterial infection, scarring or perforation. This review highlights the current literature regarding ophthalmic findings and management of CI.

Embryonic AP1 Transcription Factor Deficiency Causes a Collodion Baby-Like Phenotype

AP1 transcription factors are important controllers of gene expression in the epidermis, and altered AP1 factor function can perturb keratinocyte proliferation and differentiation. However, our understanding of how AP1 signaling changes may underlie or exacerbate skin disease is limited. We have shown that inhibiting AP1 factor function in suprabasal adult epidermis leads to reduced filaggrin levels and to a phenotype that resembles the genetic disorder ichthyosis vulgaris. We now show that inhibiting AP1 factor function during development in embryonic epidermis produces marked phenotypic changes including reduced filaggrin mRNA and protein levels, compromised barrier function, marked ultrastructural change, and enhanced dehydration susceptibility that resembles the phenotype observed in the flaky tail mouse, a model for ichthyosis vulgaris. In addition, the AP1 factor-deficient newborn mice display a collodion membrane phenotype that is not observed in flaky tail mice or in newborn individuals with ichthyosis vulgaris but is present in other forms of ichthyosis. This mixed phenotype suggests the need for a better understanding of the possible role of filaggrin loss and AP1 transcription factor deficiency in ichthyoses and collodion membrane formation.

Management of Epidermolytic Ichthyosis in the Newborn

Epidermolytic ichthyosis (EI) is a rare autosomal dominant genodermatosis that presents at birth as a bullous disease, followed by a lifelong ichthyotic skin disorder. Essentially, it is a defective keratinization caused by mutations of keratin 1 (KRT1) or keratin 10 (KRT10) genes, which lead to skin fragility, blistering, and eventually hyperkeratosis. Successful management of EI in the newborn period can be achieved through a thoughtful, directed, and interdisciplinary or multidisciplinary approach that encompasses family support. This condition requires meticulous care to avoid associated morbidities such as infection and dehydration. A better understanding of the disrupted barrier protection of the skin in these patients provides a basis for management with daily bathing, liberal emollients, pain control, and proper nutrition as the mainstays of treatment. In addition, this case presentation will include discussions on the pathophysiology, complications, differential diagnosis, and psychosocial and ethical issues.

Congenital Ichthyosiform Erythroderma Superimposed with Chronic Dermatophytosis: A Report of Three Siblings

Congenital ichthyosiform erythroderma is an autosomal recessive ichthyosis characterized by severe scaling and erythroderma. We report a family of three siblings who were all born with a collodion membrane and presented with diffuse scaling and pruritus. All three children subsequently developed chronic cutaneous dermatophyte infections requiring oral antifungals. One child developed superinfection with methicillin-resistant Staphylococcus aureus requiring antibiotics.

Isotretinoin treatment of autosomal recessive congenital ichthyosis complicated by coexisting dysferlinopathy

Consanguinity is known to be associated with an increase in the prevalence of autosomal recessive disorders such as autosomal recessive congenital ichthyosis (ARCI). ARCI often responds well to retinoid treatment. We describe a patient with ARCI who improved under isotretinoin treatment. The patient subsequently developed elevated levels of serum creatinine phosphokinase (CPK), which led to the diagnosis of a second autosomal recessive disorder, dysferlinopathy, a rare myopathy characterized by muscle weakness, decreased tendon reflexes and marked elevation of CPK levels. This report demonstrates the need for physicians to remain alert to the possible coexistence of rare and mutually relevant disorders in populations with a high rate of consanguinity.

Ichthyosis with confetti: clinics, molecular genetics and management

Ichthyosis with confetti (IWC) is an autosomal dominant congenital ichthyosis also known as ichthyosis variegata or congenital reticular ichthyosiform erythroderma. It manifests at birth with generalized ichthyosiform erythroderma or with a collodion baby picture. The erythrodermic and ichthyotic phenotype persists during life and its severity may modify. However, the hallmark of the disease is the appearance, in childhood or later in life, of healthy skin confetti-like spots, which increase in number and size with time. IWC is a very rare genodermatosis, with a prevalence <1/1,000,000 and only 40 cases reported worldwide. The most important associated clinical features include ear deformities, mammillae hypoplasia, palmoplantar keratoderma, hypertrichosis and ectropion. IWC is due to dominant negative mutations in the KRT10 and KRT1 genes, encoding for keratins 10 and keratin 1, respectively. In this context, healthy skin confetti-like spots represent “repaired” skin due to independent events of reversion of keratin gene mutations via mitotic recombination. In most cases, IWC clinical suspicion is delayed until the detection of white skin spots. Clinical features, which may represent hint to the diagnosis of IWC even before appearance of confetti-like spots, include ear and mammillae hypoplasia, the progressive development of hypertrichosis and, in some patients, of adherent verrucous plaques of hyperkeratosis. Altogether the histopathological finding of keratinocyte vacuolization and the nuclear staining for keratin 10 and keratin 1 by immunofluorescence are pathognomonic. Nevertheless, mutational analysis of KRT10 or KRT1 genes is at present the gold standard to confirm the diagnosis. IWC has to be differentiated mainly from congenital ichthyosiform erythroderma. Differential diagnosis also includes syndromic ichthyoses, in particular Netherton syndrome, and the keratinopathic ichthyoses. Most of reported IWC cases are sporadic, but familial cases with autosomal dominant mode of inheritance have been also described. Therefore, knowledge of the mutation is the only way to properly counsel the couples. No specific and satisfactory therapy is currently available for IWC. Like for other congenital ichthyoses, topical treatments (mainly emollients and keratolytics) are symptomatic and offer only temporary relief. Among systemic treatments, retinoids, in particular acitretin, improve disease symptoms in most patients. Although at present there is no curative therapy for ichthyoses, treatments have improved considerably over the years and the best therapy for each patient is always the result of both physician and patient efforts.

Epidemiology, medical genetics, diagnosis and treatment of harlequin ichthyosis in Japan

Ichthyoses are a group of disorders marked by whitish, brown or dark-brown scales on the skin of almost the whole body. Harlequin ichthyosis (HI) is the most severe form. Neonatal death from HI was once common. Due to intensive neonatal care and, probably, to the early introduction of oral retinoids, HI outcome has improved. For definitive diagnosis and the exclusion of other disorders, such as lamellar ichthyosis, which also shows a collodion baby phenotype, it is helpful to refer to electron microscopy of abnormal or absent lamellar granules and a heavy accumulation of lipid droplets in the keratinocytes. ATP-binding cassette transporter A12 (ABCA12) is known as the causative gene of HI. Severe ABCA12 deficiency results in malformation of intercellular lipid layers in the cornified layers and leads to epidermal lipid barrier disruption. In HI patients, at least one mutation on each allele must be a truncation or deletion mutation to cause serious loss of ABCA12 function. Identification of the gene underlying HI has enabled DNA-based prenatal diagnosis for HI at the earlier stages of pregnancy with low risk. There are no curative treatments for HI. Abca12-deficient mice were created as a model of HI. Treatment of the model mice with retinoid or steroid has not been successful.

Targeting epidermal lipids for treatment of Mendelian disorders of cornification

BACKGROUND

Inherited ichthyoses or Mendelian disorders of cornification (MeDOC) are clinically heterogeneous disorders with high unmet therapeutic needs, which are characterized by skin hyperkeratosis and scaling. Some MeDOC types are associated with defects of the epidermal lipid metabolism, resulting in perturbed barrier permeability and subsequent epidermal hyperplasia, hyperkeratosis and inflammation. An example is the CHILD (congenital hemidysplasia with ichthyosiform nevus and limb defects) syndrome, an X-linked dominant multisystem MeDOC caused by mutations in the NSDHL (NAD(P)H steroid dehydrogenase-like protein) gene, which is involved in the distal cholesterol biosynthetic pathway. The skin manifestations of the CHILD syndrome have been attributed to two major mechanisms: deficiency of cholesterol, probably influencing the proper corneocyte membrane formation, and toxic accumulation of aberrant steroid precursors.

METHODS

Here we addressed the efficacy of an ointment containing cholesterol and simvastatin, an agent inhibiting endogenous cholesterol synthesis in a compassionate-use treatment of three patients with CHILD syndrome. To test the specificity of this therapeutic approach, we applied the same topical treatment to two patients with other types of MeDOC with disturbed skin lipid metabolism.

RESULTS

The therapy with simvastatin and cholesterol was highly effective and well-tolerated by the CHILD syndrome patients; only lesions in the body folds represented a therapeutic challenge. No improvement was noted in the patients with other types of MeDOC.

CONCLUSIONS

This therapy is inexpensive and accessible to every patient with CHILD syndrome, because both simvastatin and cholesterol are available worldwide. Our data provide initial evidence of the specificity of the therapeutic effect of the simvastatin-cholesterol ointment in CHILD syndrome in comparison to other types of MeDOC.

Prevalence of inherited ichthyosis in France: a study using capture-recapture method

BACKGROUND

Inherited ichthyoses represent a group of rare skin disorders characterized by scaling, hyperkeratosis and inconstant erythema, involving most of the tegument. Epidemiology remains poorly described. This study aims to evaluate the prevalence of inherited ichthyosis (excluding very mild forms) and its different clinical forms in France.

METHODS

Capture - recapture method was used for this study. According to statistical requirements, 3 different lists (reference/competence centres, French association of patients with ichthyosis and internet network) were used to record such patients. The study was conducted in 5 areas during a closed period.

RESULTS

The prevalence was estimated at 13.3 per million people (/M) (CI95%, [10.9 - 17.6]). With regard to autosomal recessive congenital ichthyosis, the prevalence was estimated at 7/M (CI 95% [5.7 - 9.2]), with a prevalence of lamellar ichthyosis and congenital ichthyosiform erythroderma of 4.5/M (CI 95% [3.7 - 5.9]) and 1.9/M (CI 95% [1.6 - 2.6]), respectively. Prevalence of keratinopathic forms was estimated at 1.1/M (CI 95% [0.9 - 1.5]). Prevalence of syndromic forms (all clinical forms together) was estimated at 1.9/M (CI 95% [1.6 - 2.6]).

CONCLUSIONS

Our results constitute a crucial basis to properly size the necessary health measures that are required to improve patient care and design further clinical studies.

Pathogenesis-based therapies in ichthyoses

During the past 20 years, tremendous progress has been made in our understanding of the molecular basis of many genetic skin conditions. The translation of these laboratory findings into effective therapies for affected individuals has been slow, however, in large part due to the risk of carcinogenesis from random viral genomic integration and the lack of efficacy of topically applied genetic material and most proteins. As intervention at the gene level still appears remote for most genetic disorders, increased knowledge about the cellular and biochemical pathogenesis of disease allows specific targeting of pathways with existing and/or novel drugs and molecules. In contrast to the requirement for personalization of most gene-based approaches, pathogenesis-based therapy is pathway specific, and in theory, it should have broader applicability. In this chapter, we provide an overview of the pathoetiology of the various types of ichthyoses and demonstrate how a pathogenesis-based approach can potentially lead to innovative treatments for these conditions. Notably, this strategy has been successfully validated for the treatment of the rare X-linked dominant condition, CHILD syndrome, in which topical applications of cholesterol and lovastatin together to affected skin resulted in marked improvement of the skin phenotype.