Revised nomenclature and classification of inherited ichthyoses: results of the First Ichthyosis Consensus Conference in Sorèze 2009

Alopecia patterns and trichoscopic findings in patients with autosomal recessive congenital ichthyosis

Background

Autosomal recessive congenital ichthyosis (ARCI) is a rare genodermatosis categorized among nonsyndromic ichthyoses. While ARCI patients often manifest hair abnormalities, their impact on the quality of life remains underreported in the literature.

Objective

This study aims to comprehensively characterize the clinical and trichoscopic findings of alopecia in ARCI patients.

Methods

A prospective study spanning from January 2019 to December 2021 (3 years) was conducted at the Dermatology Department of Habib Thameur Hospital, Tunis, Tunisia. Clinical and trichoscopic examinations were performed on the hair of the participants, with molecular studies conducted on 15 patients.

Results

The study included 30 patients, predominantly female (male/female = 0.58), with a mean age of 20 years. Twenty-eight patients were born from consanguineous marriages. Lamellar ichthyosis was observed in 22 cases, while congenital ichthyosiform erythroderma and bathing suit ichthyosis were each present in 4 cases. The ARCI severity score, assessed using the Visual Index For Ichthyosis Severity scale, had a mean value of 15 (4-28). Alopecia emerged as a prominent finding in 11 patients, presenting as hairline recession (13%), multiple patchy alopecia (27%), and alopecia of the eyebrows (13%). Trichoscopic findings included interfollicular and perifollicular scaling, perifollicular lamellar hyperkeratosis, peripilar casts, interfollicular erythema, loss of hair openings, predominance of single hair follicles, broken hair, vellus hair, anisotrichosis, pili torti, dystrophic hair, and comma hair. Several trichoscopic findings showed statistically significant associations with the severity of ARCI.

Limitations

In our study, we only included 30 patients due to the rarity of this genodermatosis.

Conclusion

Contrary to previous perceptions, alopecia is a notable finding in ARCI, particularly in patients with a severe form. This study provides a detailed characterization of alopecia in ARCI, shedding light on its prevalence and associated trichoscopic features, thereby enhancing our understanding of this dermatological condition.

Heterozygous DSP in-frame deletion in a poodle with syndromic ichthyosis involving additional hair and tooth abnormalities

Ichthyoses comprise a large heterogeneous group of skin disorders, characterized by generalized scaly and hyperkeratotic skin. We investigated a miniature poodle with early onset generalized scaling, dry and irregularly thickened skin, paw pad hyperkeratosis and abnormalities in hair and teeth. The clinical signs of ichthyosis were confirmed by histopathological examination, which revealed mild epidermal hyperplasia and lamellar orthokeratotic hyperkeratosis. A hereditary condition was suspected and a genetic investigation was initiated. We sequenced the whole genome of the affected dog and searched for potentially causative variants in functional candidate genes for the observed phenotype. The analysis revealed a heterozygous in-frame deletion in DSP, NC_049256.1:g.8804542_8804544del resulting from a de novo mutation event as evidenced by genotyping leukocyte DNA from both parents. The 3 bp deletion is predicted to remove one aspartic acid without disrupting the open reading frame (XM_038584124.1:c.1821_1823del, XP_038440052.1:p.(Asp608del)). The DSP gene encodes desmoplakin, a desmosomal plaque protein, responsible for cell-cell adhesion to provide resistance to mechanical stress in epidermal and cardiac tissues. We hypothesize that the deletion of one amino acid in the N-terminal globular head domain acts in a dominant negative manner and thus impairs the proper connection with other proteins. Several variants in DSP in humans and cattle have been described to result in different phenotypes associated with hair and skin abnormalities, sometimes in combination with variable cardiac and/or dental manifestations. In conclusion, we characterized a new syndromic ichthyosis phenotype in a dog and identified a de novo 3 bp deletion in the DSP gene as causal variant.

A cellular disease model toward gene therapy of TGM1-dependent lamellar ichthyosis

Lamellar ichthyosis (LI) is a chronic disease, mostly caused by mutations in the TGM1 gene, marked by impaired skin barrier formation. No definitive therapies are available, and current treatments aim at symptomatic relief. LI mouse models often fail to faithfully replicate the clinical and histopathological features of human skin conditions. To develop advanced therapeutic approaches, such as combined ex vivo cell and gene therapy, we established a human cellular model of LI by efficient CRISPR-Cas9-mediated gene ablation of the TGM1 gene in human primary clonogenic keratinocytes. Gene-edited cells showed complete absence of transglutaminase 1 (TG1) expression and recapitulated a hyperkeratotic phenotype with most of the molecular hallmarks of LI in vitro. Using a self-inactivating γ-retroviral (SINγ-RV) vector expressing transgenic TGM1 under the control of its own promoter, we tested an ex vivo gene therapy approach and validate the model of LI as a platform for pre-clinical evaluation studies. Gene-corrected TGM1-null keratinocytes displayed proper TG1 expression, enzymatic activity, and cornified envelope formation and, hence, restored proper epidermal architecture. Single-cell multiomics analysis demonstrated proviral integrations in holoclone-forming epidermal stem cells, which are crucial for epidermal regeneration. This study serves as a proof of concept for assessing the potential of this therapeutic approach in treating TGM1-dependent LI.

Highlights of Gene and Cell Therapy for Epidermolysis Bullosa and Ichthyosis

Advancements in the molecular genetics of epidermolysis bullosa (EB) and ichthyosis, two rare inherited skin conditions, have enabled the identification of genetic variants that cause these diseases. Alongside technological advancements in genetic medicine, the identification of variants causal of these rare skin conditions has led to preclinical research and the clinical development of various in vivo and ex vivo gene and cell therapies for their treatment. Gene and cell therapies are considered to be the most advanced forms of personalized medicine, demonstrating safety and efficacy in numerous rare diseases. Although the orphan drug development boom has resulted in regulatory approval of multiple gene and cell therapies for various rare conditions, the application of these modalities to rare inherited skin conditions remains limited. Nonetheless, there are successful examples of both in vivo gene therapy- and ex vivo cell therapy-based approaches developed to treat EB and ichthyosis. This review highlights preclinical research and the clinical development of gene and cell therapies for multiple subtypes of these two devastating congenital skin conditions, including a gene therapy recently approved by the U.S. Food and Drug Administration for the treatment of recessive dystrophic EB.

Personal, financial and time burden in inherited ichthyoses: A survey of 144 patients in a university-based setting

BACKGROUND

Patients with inherited ichthyosis suffer from scaling due to mutations affecting the epidermal barrier. Symptomatic treatment with ointments, bathing and mechanical scale removal can alleviate the disease, but therapy is time and cost intensive.

OBJECTIVES

We investigated costs, time and disease burden of ichthyoses. The study addresses difficulties of the healthcare situation for patients with ichthyoses and reveals potential improvements.

MATERIALS AND METHODS

We developed a questionnaire addressing time and financial effort for the treatment. Additionally, we collected data of the Dermatology Life Quality Index (DLQI) and the Pruritus Life Quality (5PLQ) questionnaires to determine the impact of ichthyosis and associated pruritus on quality of life (QoL).

RESULTS

We recruited 144 patients with ichthyosis (median age: 23; 53.5% female) from the Department of Dermatology in Muenster (Germany) and the German patient support group including common, rare and syndromic subtypes. Eighty-seven percent reported applying topical therapeutics at least once per day, 66.4% several times with an overall median duration of 15 min. Highest single expenditure of time was due to balneotherapy (n = 115; median bathing time: 40 min). In 81.9%, the health insurance did not completely cover the costs for topical treatment causing additional financial burden to the patient with a median of 71 € per quarter, herein creams being the largest cost factor (50 €). Patients with Netherton syndrome showed the highest median expenditure (170 €). The QoL impairment under treatment was moderate (median DLQI: 8.5 points). Pruritus was prevalent in 79.9% and showed a distinct impact on QoL (median 5PLQ: 7.5 points) without any significant difference between the subtypes (p = 0.37).

CONCLUSION

Patients suffering from ichthyoses have a large and lifelong overall burden in mild and severe subtypes. Since continuous topical treatment is required, financial and psychosocial support needs to be considered beyond dermatological care.

Treating epidermolytic ichthyosis and ichthyosis with confetti with epidermal autografts cultured from revertant skin

BACKGROUND

No efficient treatment has yet been established for epidermolytic ichthyosis (EI), which is caused by pathogenic variants of KRT1 or KRT10. Patients with ichthyosis with confetti (IWC) have multiple normal-appearing spots, caused by the revertant somatic recombination of pathogenic variants that occurs at each spot independently. Additionally, some patients with EI have large areas of normal skin due to revertant postzygotic mosaicism.

OBJECTIVES

To assess the feasibility of transplanting cultured epidermal autografts (CEAs) produced from revertant epidermal keratinocytes in patients with EI and IWC.

METHODS

We performed a clinical trial of treatment with CEAs produced from each patient's own revertant epidermal keratinocytes as a proof-of-concept study. This was a single-arm, open, unmasked, uncontrolled, single-assignment, treatment-purpose study. The primary outcome was the percentage area that lacked recurrence of ichthyosis lesions 4 weeks after the final transplant. The secondary outcome was the percentage area lacking recurrence of ichthyosis lesions 24 weeks after the initial transplantation. The trial was registered with the Japan Registry of Clinical Trials (jRCTb041190097).

RESULTS

We successfully produced CEAs from genetically confirmed revertant skin from two patients with mosaic EI and from one patient with IWC and confirmed by amplicon sequencing and droplet digital polymerase chain reaction analysis that the CEAs mainly consisted of revertant wild-type cells. Single-cell RNA sequencing analysis confirmed the normal proliferation and safety profiling of CEAs. CEAs were transplanted onto desquamated lesional sites in the patients. Four weeks post-transplantation, the percentage area lacking recurrence of ichthyosis lesions in the three patients was 40%, 100% and 100% respectively, although recurrence of ichthyosis lesions was seen at the site of CEA transplantation in all three patients at 24 weeks post-transplantation.

CONCLUSIONS

CEAs from normal skin have the potential to be a safe and local treatment option for EI and IWC.

Genetic testing and new variants in diagnosis of congenital ichthyoses

BACKGROUND

The aim of this study was to evaluate how diagnostic practice in congenital ichthyoses has evolved during the years 2000-2020 and what kind of gene variants of congenital ichthyosis have been found.

METHODS

The study cohort of this register-based research consisted of a total of 88 patients, whose diagnostic testing was conducted, and ichthyosis diagnoses set at the Department of Dermatology and the Department of Clinical Genetics at Tampere University Hospital during the years 2000-2020.

RESULTS

Diagnosis of ichthyosis was confirmed with genetic testing in 33 cases, and with conventional diagnostic methods, such as clinical findings, skin biopsy and family history of ichthyoses, in 55 cases. We observed four novel variants in patients with the clinical diagnoses of congenital ichthyoses.

CONCLUSION

When genetic testing became available, it was offered primarily to patients with severe forms of ichthyosis. During the study period next-generation sequencing became the genetic testing method of choice providing new opportunities in diagnostics.

Revisiting X-linked congenital ichthyosis

X-linked recessive ichthyosis (XLI) is a hereditary skin disease characterized by generalized dryness and scaling of the skin, with frequent extracutaneous manifestations. It is the second most common type of ichthyosis, with a prevalence of 1/6,000 to 1/2,000 in males and without any racial or geographical differences. The causative gene for XLI is the steroid sulfatase gene (STS), located on Xp22.3. STS deficiency causes an abnormal cholesterol sulfate (CS) accumulation in the stratum corneum (SC). Excess CS induces epidermal permeability barrier dysfunction and scaling abnormalities. This review summarizes XLI's genetic, clinical, and pathological features, pathogenesis, diagnosis and differential diagnoses, and therapeutic perspectives. Further understanding the role of the STS gene pathogenic variants in XLI may contribute to a more accurate and efficient clinical diagnosis of XLI and provide novel strategies for its treatment and prenatal diagnosis.

Prevalence of ichthyoses in Denmark: a nationwide registry-based study

The results demonstrate a prevalence of 1.6 per 10 000 for all types of ichthyoses, based on large Danish national patient registries, including all patients with relevant diagnoses alive on 31 December 2021. A study of this size and depth has not been completed before but may still underestimate the prevalence and potential burden of the diseases.

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.

Epidermolytic ichthyosis: Clinical spectrum and burden of disease in a large German cohort

BACKGROUND

Keratinopathic ichthyoses are a group of hereditary skin disorders caused by pathogenic variants in keratin genes such as KRT1, KRT2 and KRT10, resulting in conditions such as epidermolytic ichthyosis (EI), autosomal-recessive EI, superficial EI and epidermal nevus. Case reports highlight the diversity of clinical manifestations, but only limited information exists regarding the quality of life and burden of disease.

OBJECTIVES

The objective of this study was to assess the clinical spectrum, genotype-phenotype correlations and burden of disease in patients with epidermolytic ichthyosis in Germany.

METHODS

We conducted an observational study involving 48 patients diagnosed with EI. Evaluations included the severity of skin involvement using the Investigator's Global Assessment (IGA), the modified Ichthyosis Area Severity Index (mIASI) and complications. The burden of disease was evaluated using the Dermatology Life Quality Index (DLQI) or the Children's Dermatology Life Quality Index (cDLQI).

RESULTS

Based on clinical features, mIASI and IGA, EI can be categorized into localized, intermediate and severe forms. Patients with keratin 1 mutations tended to have severe EI, while the three forms were evenly distributed in those with keratin 10 mutations. The study highlights that around half of the patients with EI experienced itch and severe pain. Quality of life was affected, with daily life restrictions of 78% due to care and therapies. Reimbursement for moisturizing ointments by health insurance was insufficient for one-quarter of cases.

CONCLUSIONS

The results emphasize the need for targeted interventions and comprehensive care strategies to enhance the quality of life for affected individuals.

Challenges and progress related to gene editing in rare skin diseases

Genodermatoses represent a large group of inherited skin disorders encompassing clinically-heterogeneous conditions that manifest in the skin and other organs. Depending on disease variant, associated clinical manifestations and secondary complications can severely impact patients' quality of life and currently available treatments are transient and not curative. Multiple emerging approaches using CRISPR-based technologies offer promising prospects for therapy. Here, we explore current advances and challenges related to gene editing in rare skin diseases, including different strategies tailored to mutation type and structural organization of the affected gene, considerations for in vivo and ex vivo applications, the critical issue of delivery into the skin, and immune aspects of therapy. Against the backdrop of a landmark FDA approval for the first re-dosable gene replacement therapy for a rare genetic skin disorder, gene editing approaches are inching closer to the clinics and the possibility of a local permanent cure for patients affected by these disorders.

Compound heterozygous ABCA12 variants identified in a Chinese patient with congenital ichthyosiform erythroderma: Advancing genotype-phenotype correlations and literature review

BACKGROUND

Ichthyosis is a common keratotic skin disease with high clinical, etiological and genetic heterogeneity. There are four types of non-syndromic hereditary ichthyoses, among which autosomal recessive congenital ichthyosis (ARCI) is a heterogeneous group of recessive Mendelian disorders. ARCI present with different phenotypes and ABCA12 pathogenic variants have been shown to cause complex ARCI phenotypes, including harlequin ichthyosis (HI), lamellar ichthyosis (LI) and congenital ichthyosiform erythroderma (CIE).

METHODS

A sporadic male patient, clinically diagnosed with CIE, was enrolled in this study. Exome sequencing was combined with Sanger sequencing to confirm the diagnosis and identify the pathogenic variants. In silico predictions were made using multiple software programs, and the identified variants were interpreted using the ACMG guidelines. A review of all literature reported ABCA12 variants was performed to explore genotype-phenotype correlations.

RESULTS

Compound heterozygous ABCA12 variants [c.5381+1G>A and c.5485G>C (p.Asp1829His)] (NM_173076) were identified. The two variants were not detected in the public database. c.5381+1G>A is predicted to affect ABCA12 mRNA splicing and Asp1829 is highly conserved among various species. In silico analysis suggested that these two variants were responsible for the phenotype of the patient. Genotype-phenotype correlation analysis showed that biallelic truncation variants and/or exon/amino acid deletions in ABCA12 are the most common causes of HI. Biallelic missense variants are most common in LI and CIE.

CONCLUSIONS

The compound heterozygous ABCA12 variants caused the CIE phenotype observed in the patient. The spectrum of ABCA12 pathogenic variants were broaden. Genotype-phenotype correlation analysis provided detailed evidence which can be used in future prenatal diagnosis and can inform the need for genetic counselling for patients with ABCA12-related ARCIs.

Autosomal Dominant Lamellar Ichthyosis Due to a Missense Variant in the Gene NKPD1

The identification of monogenic causes for cornification disorders has enhanced our understanding of epidermal differentiation and skin barrier function. Autosomal dominant lamellar ichthyosis is a rare condition, and ASPRV1 was the only gene linked to autosomal dominant lamellar ichthyosis to date. We identified a heterozygous variant (ENST00000686631.1:c.1372G>T, p.[Val458Phe]) in the NKPD1 gene in 7 individuals from a 4-generation German pedigree with generalized lamellar ichthyosis by whole-exome sequencing. Segregation analysis confirmed its presence in affected individuals, resulting in a logarithm of the odds score of 3.31. NKPD1 encodes the NKPD1 protein, implicated in the plasma membrane; its role in human disease is as yet unknown. Skin histology showed moderate acanthosis and compact orthohyperkeratosis, and the ultrastructure differed clearly from that in ASPRV1-autosomal dominant lamellar ichthyosis. Although NKPD1 mRNA expression increased during keratinocyte differentiation, stratum corneum ceramides exhibited no significant changes. However, affected individuals showed an elevated ratio of protein-bound ceramides to omega-esterified ceramides. This highlights NKPD1's role in autosomal dominant lamellar ichthyosis, impacting ceramide metabolism and skin lipid barrier formation, as demonstrated through functional characterization.

Altered skin microbiome, inflammation, and JAK/STAT signaling in Southeast Asian ichthyosis patients

BACKGROUND

Congenital ichthyosis (CI) is a collective group of rare hereditary skin disorders. Patients present with epidermal scaling, fissuring, chronic inflammation, and increased susceptibility to infections. Recently, there is increased interest in the skin microbiome; therefore, we hypothesized that CI patients likely exhibit an abnormal profile of epidermal microbes because of their various underlying skin barrier defects. Among recruited individuals of Southeast Asian ethnicity, we performed skin meta-genomics (i.e., whole-exome sequencing to capture the entire multi-kingdom profile, including fungi, protists, archaea, bacteria, and viruses), comparing 36 CI patients (representing seven subtypes) with that of 15 CI age-and gender-matched controls who had no family history of CI.

RESULTS

This case-control study revealed 20 novel and 31 recurrent pathogenic variants. Microbiome meta-analysis showed distinct microbial populations, decreases in commensal microbiota, and higher colonization by pathogenic species associated with CI; these were correlated with increased production of inflammatory cytokines and Th17- and JAK/STAT-signaling pathways in peripheral blood mononuclear cells. In the wounds of CI patients, we identified specific changes in microbiota and alterations in inflammatory pathways, which are likely responsible for impaired wound healing.

CONCLUSIONS

Together, this research enhances our understanding of the microbiological, immunological, and molecular properties of CI and should provide critical information for improving therapeutic management of CI patients.

Cross-Sectional Study on Autosomal Recessive Congenital Ichthyoses: Association of Genotype with Disease Severity, Phenotypic, and Ultrastructural Features in 74 Italian Patients

BACKGROUND

Autosomal recessive congenital ichthyoses (ARCIs) are a clinically heterogeneous group of keratinization disorders characterized by generalized skin scaling due to mutations in at least 12 genes. The aim of our study was to assess disease severity, phenotypic, and ultrastructural features and to evaluate their association with genetic findings in ARCI patients.

METHODS

Clinical signs and symptoms, and disease severity were scored in a single-center series of patients with a genetic diagnosis of ARCI. Skin ultrastructural findings were reviewed.

RESULTS

Seventy-four consecutive patients (mean age 11.0 years, range 0.1-48.8) affected with lamellar ichthyosis (50/74, 67.5%), congenital ichthyosiform erythroderma (18/74, 24.3%), harlequin ichthyosis (two/74, 2.7%), and other minor ARCI subtypes (four/74, 5.4%) were enrolled. Mutated genes were as follows: TGM1 in 18/74 (24.3%) patients, ALOX12B in 18/74 (24.3%), CYP4F22 in 12/74 (16.2%), ABCA12 in nine/74 (12.2%), ALOXE3 in seven/74 (9.5%), NIPAL4 in seven/74 (9.5%), and CERS3, PNPLA1, and SDR9C7 in 1 patient each (1.4%). Twenty-five previously undescribed mutations in the different ARCI causative genes, as well as two microduplications in TGM1, and two microdeletions in CYP4F22 and NIPAL4 were identified. The mean ichthyosis severity score in TGM1- and ABCA12-mutated patients was significantly higher than in all other mutated genes, while the lowest score was observed in CYP4F22-mutated patients. Alopecia, ectropion, and eclabium were significantly associated with TGM1 and ABCA12 mutations, and large, thick, and brownish scales with TGM1 mutations. Among specific phenotypic features, psoriasis-like lesions as well as a trunk reticulate scale pattern and striated keratoderma were present in NIPAL4-mutated patients. Ultrastructural data available for 56 patients showed a 100% specificity of cholesterol clefts for TGM1-mutated cases and revealed abnormal lamellar bodies in SDR9C7 and CERS3 patients.

CONCLUSION

Our study expands the phenotypic and genetic characterization of ARCI by the description of statistically significant associations between disease severity, specific clinical signs, and different mutated genes. Finally, we highlighted the presence of psoriasis-like lesions in NIPAL4-ARCI patients as a novel phenotypic feature with diagnostic and possible therapeutic implications.

Updated mutational spectrum and genotype-phenotype correlations in ichthyosis patients with ABCA12 pathogenic variants

Autosomal recessive congenital ichthyoses (ARCI) is a genetically heterogeneous condition that can be caused by pathogenic variants in at least 12 genes, including ABCA12. ARCI mainly consists of congenital ichthyosiform erythroderma (CIE), lamellar ichthyosis (LI) and harlequin ichthyosis (HI). The objective was to determine previously unreported pathogenic variants in ABCA12 and to update genotype-phenotype correlations for patients with pathogenic ABCA12 variants. Pathogenic variants in ABCA12 were detected using Sanger sequencing or a combination of Sanger sequencing and whole-exome sequencing. To verify the pathogenicity of a previously unreported large deletion and intron variant, cDNA analysis was performed using total RNA extracted from hair roots. Genetic analyses were performed on the patients with CIE, LI, HI and non-congenital ichthyosis with unusual phenotypes (NIUP), and 11 previously unreported ABCA12 variants were identified. Sequencing of cDNA confirmed the aberrant splicing of the variant ABCA12 in the patients with the previously unreported large deletion and intron variant. Our findings expand the phenotype spectrum of ichthyosis patients with ABCA12 pathogenic variants. The present missense variants in ABCA12 are considered to be heterogenous in pathogenicity, and they lead to varying disease severities in patients with ARCI and non-congenital ichthyosis with unusual phenotypes (NIUP).

Autosomal recessive ALOX12B gene and consecutive collodion baby

Autosomal recessive congenital ichthyosis is a type of inherited ichthyosis which is a rare cluster of genetic disorders leading to defective keratinisation. The combined prevalence for lamellar ichthyosis and congenital ichthyosiform erythroderma is almost 1 per 200 000-300 000 people. Among all the mutations in this gene, missense and frameshift mutations are most common which account for 80% of the cases. Our patient had a mutation in R-type arachidonate 12-lipoxygenase gene (ALOX12B, OMIM*603741).

Clinico-Epidemiologic Profile of Non-Syndromic Congenital Ichthyosis - A Retrospective Chart Review of 107 Patients

Background

Congenital ichthyoses are a rare Mendelian group of disorders affecting the integument with a heterogeneous clinical presentation amongst which scaling is a constant feature. There is scanty epidemiologic data regarding the clinical profile and histologic patterns of inherited ichthyosis from resource-poor countries.

Aims and Objectives

The study was aimed at assessing the clinic-epidemiologic characteristics associated with the different forms of non-syndromic congenital ichthyosis.

Materials and Methods

This was a retrospective chart review of ichthyosis patients that presented between July 2016 and Jun 2020. Details including demographic profile, clinical characteristics along with any relevant investigations done were included.

Results

During the study period of 4 years, 107 patients with congenital non-syndromic ichthyosis were seen. The most frequent diagnosis was of common ichthyoses, followed by autosomal recessive congenital ichthyosis, epidermolytic ichthyosis and erythrokeratoderma, in decreasing order.

Conclusion

Important clinical findings like erythema and the type of scales as well as histological differences including an absent or reduced granular layer in ichthyosis vulgaris can help differentiate among the clinical phenotypes of inherited non-syndromic ichthyosis especially in resource-poor settings. Also, there is a high prevalence of vitamin D deficiency and hence a need for screening for the same in all patients of congenital ichthyosis including the milder phenotypes.

French national protocol for the management of congenital ichthyosis

Congenital ichthyoses (CI) comprise a heterogeneous group of monogenic genetic skin diseases characterized by diffuse scaling, often associated with skin inflammation. Diagnosis of the individual form of ichthyosis is complex and is guided by clinical expertise. CI usually has a major impact on quality of life (QOL) and thus requires lifelong treatment. To date, there are no curative therapies, although various symptomatic treatment options exist. The present protocol for the management of CI has been drawn up in accordance with the recommendations published in 2012 by the French National Authority for Health, based on a literature review, with the help and validation of members of the French network for rare skin diseases (FIMARAD). It provides a summary of evidence and expert-based recommendations and is intended to help clinicians with the management of these rare and often complex diseases.

Congenital Ichthyosis: Current Approaches to Prenatal Diagnoses

INTRODUCTION

Congenital ichthyosis represents a wide spectrum of diseases. This article reviews prenatal testing for ichthyosis.

METHODS

We used pubmed.ncbi.nlm.nih.gov to search for 38 types of congenital ichthyosis combined with 17 words related to prenatal testing.

RESULTS

Search resulted in 408 publications covering 13 types of ichthyoses and four types of tests.

DISCUSSION

Biochemical testing is diagnostic in trichothiodystrophy, but nonspecific in X-linked ichthyosis and Refsum syndrome. Except in X-linked ichthyosis, biochemical testing requires invasive procedures to obtain fetal skin biopsy, amniocytes, or chorionic villus samples. It is superior to histological and cytological examination of fetal skin biopsy or amniocytes because keratinization occurs later in pregnancy and microscopy cannot differentiate between ichthyosis types. Imaging is more acceptable due to noninvasiveness and routine use, although ultrasonography is operator-dependent, nonspecific, and captures abnormalities at late stage. Molecular tests are described in at-risk pregnancies but testing of free fetal DNA was not described.

Syndromic or non-syndromic congenital ichthyosis? A case report of two brothers with ichthyosis but microphthalmia and blindness in only one brother

We present the cases of two brothers with ichthyosis, born to consanguineous parents, with the eldest having extracutaneous manifestations in the form of microphthalmia and corneal opacities causing complete blindness. Initially, we were faced with the question of whether the phenotype in this family was due to the effects of a single pleiotropic, presumably autosomal recessive gene manifesting as a syndromic form of ichthyosis, or whether there were multiple causal genes, and the ichthyosis was non-syndromic. Ultimately, clinical follow-up of the family, combined with research-based exome sequencing established a diagnosis of NIPAL4 autosomal recessive congenital ichthyosis in both brothers, but the ocular abnormalities causing blindness in the older brother were due to coexisting autosomal recessively inherited loss of function mutations in peroxidasin, the latter finding also seen in a sister unaffected by ichthyosis.

Cross-sectional nationwide epidemiologic survey on quality of life and treatment efficacy in Japanese patients with congenital ichthyoses

BACKGROUND

Congenital ichthyoses sometimes present with severe skin symptoms that significantly affect the patient's quality of life (QOL). Symptomatic treatments are the mainstay therapies, and their efficacy is limited and inadequate.

OBJECTIVE

To assess the disease severity and QOL in patients with congenital ichthyoses, and to investigate the effectiveness of current treatments.

METHODS

We conducted a questionnaire-based Japan-wide epidemiological survey of patients with congenital ichthyosis who received medical care from 1 January 2016-31 December 2020. Effectiveness of past and current treatments was assessed. The outcomes were the physician's assessment, disease severity assessed using the clinical ichthyosis score (CIS), and the disease burden estimated using the Dermatology Life Quality Index (DLQI), the Children's Dermatology Life Quality Index (CDLQI), and the Infants' Dermatitis Quality of Life Index.

RESULTS

One hundred patients with 14 ichthyosis subtypes from 47 institutes were included in the final analysis. The CDLQI score showed a positive correlation with CIS (rs = 0.59, p = 0.004), while the DLQI score showed no significant correlation (rs = 0.13, p = 0.33). All existing medications were effective for many patients. Etretinate improved QOL and reduced CIS, but side effects including bone growth retardation were reported. Decreased treatment willingness was observed in patients with very low and very high CIS.

CONCLUSION

QOL scores were found to correlate with CIS in children, but not in adults. Considering the adverse events, it is speculated that etretinate is not indicated for children with mild cases. Petrolatum was the most commonly used medication, even in patients who were reluctant to receive treatment.

Lipid Nanoparticle-Mediated Hit-and-Run Approaches Yield Efficient and Safe In Situ Gene Editing in Human Skin

Despite exciting advances in gene editing, the efficient delivery of genetic tools to extrahepatic tissues remains challenging. This holds particularly true for the skin, which poses a highly restrictive delivery barrier. In this study, we ran a head-to-head comparison between Cas9 mRNA or ribonucleoprotein (RNP)-loaded lipid nanoparticles (LNPs) to deliver gene editing tools into epidermal layers of human skin, aiming for in situ gene editing. We observed distinct LNP composition and cell-specific effects such as an extended presence of RNP in slow-cycling epithelial cells for up to 72 h. While obtaining similar gene editing rates using Cas9 RNP and mRNA with MC3-based LNPs (10-16%), mRNA-loaded LNPs proved to be more cytotoxic. Interestingly, ionizable lipids with a pKa ∼ 7.1 yielded superior gene editing rates (55%-72%) in two-dimensional (2D) epithelial cells while no single guide RNA-dependent off-target effects were detectable. Unexpectedly, these high 2D editing efficacies did not translate to actual skin tissue where overall gene editing rates between 5%-12% were achieved after a single application and irrespective of the LNP composition. Finally, we successfully base-corrected a disease-causing mutation with an efficacy of ∼5% in autosomal recessive congenital ichthyosis patient cells, showcasing the potential of this strategy for the treatment of monogenic skin diseases. Taken together, this study demonstrates the feasibility of an in situ correction of disease-causing mutations in the skin that could provide effective treatment and potentially even a cure for rare, monogenic, and common 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.

[Scaling skin in infancy]

An infant was admitted to the neonatal intensive care unit due to a noticeable desquamation of the skin in the groin, extremities and axillary regions. In addition to the desquamation the baby had a collodion membrane. Microbiological swabs taken of the affected areas, however, did not show any microbial growth. Even in the molecular analysis, no common mutation for congenital ichthyoses could be found. The self-healing collodion baby (SHCB) is one subtype of autosomal recessive inherited ichthyoses. In mild courses watchful waiting and a moisturizing cream is justified.

Novel Compound Heterozygous Mutations of TGM1 Gene Identified in a Turkish Collodion Baby Diagnosed with Non-Bullous Congenital Ichthyosiform Erythroderma

Autosomal recessive congenital ichthyosis (ARCI) is a group of diseases presenting as collodion baby at birth. ARCI is categorized as Harlequin ichthyosis, lamellar ichthyosis, and non-bullous congenital ichthyosiform erythroderma (NBCIE), bathing suit icthyosis (BSI) and others. We describe the case of a male newborn with NBCIE whose whole exome sequencing revealed two variants of TGM1 gene (NM_000359.3) in a compound heterozygous state: c.790C>T (p.Arg264Trp) in exon 5 and c.2060G>A (p.Arg687His) in exon 13. In the literature, the Arg264Trp variant has been reported as homozygous or compound heterozygous with other variants in patients with BSI. In contrast, the Arg687His variant has been reported only as homozygous in patients with BSI. To the best of our knowledge, this is the first case whose two compound heterozygous variants, exhibiting the NBCIE phenotype, instead of the BSI.

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.

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.

Next-generation sequencing in dermatology

Over the past decade, Next-Generation Sequencing (NGS) has advanced our understanding, diagnosis, and management of several areas within dermatology. NGS has emerged as a powerful tool for diagnosing genetic diseases of the skin, improving upon traditional PCR-based techniques limited by significant genetic heterogeneity associated with these disorders. Epidermolysis bullosa and ichthyosis are two of the most extensively studied genetic diseases of the skin, with a well-characterized spectrum of genetic changes occurring in these conditions. NGS has also played a critical role in expanding the mutational landscape of cutaneous squamous cell carcinoma, enhancing our understanding of its molecular pathogenesis. Similarly, genetic testing has greatly benefited melanoma diagnosis and treatment, primarily due to the high prevalence of BRAF hot spot mutations and other well-characterized genetic alterations. Additionally, NGS provides a valuable tool for measuring tumor mutational burden, which can aid in management of melanoma. Lastly, NGS demonstrates promise in improving the sensitivity of diagnosing cutaneous T-cell lymphoma. This article provides a comprehensive summary of NGS applications in the diagnosis and management of genodermatoses, cutaneous squamous cell carcinoma, melanoma, and cutaneous T-cell lymphoma, highlighting the impact of NGS on the field of dermatology.

Advanced Anterior Eye Segment Imaging for Ichthyosis

The purpose of this study was to describe ocular surface and anterior eye segment findings in various types of ichthyoses.

METHODS

This was a single-center prospective observational study. The study group consisted of five patients (P1-P5) aged 13-66 years. Multimodal imaging was performed, including slit-lamp examinations, swept-source optical coherence tomography (SS-OCT), and in vivo confocal microscopy (IVCM).

RESULTS

All patients were diagnosed with moderate-to-severe dry eye disease (DED). The corneas showed a significant pattern of irregularity, with a significant difference between the corneal thickness at the apex (CAT) and the corneal thinnest thickness (CTT), exceeding 375 µm. Three patients were diagnosed with ectasia patterns based on SS-OCT. All patients showed abnormalities in at least one Fourier index parameter for at least one eye at 3 or 6 mm in the keratometric, anterior, or posterior analyses. IVCM examinations revealed changes in all corneal layers.

CONCLUSIONS

By combining the results of multimodal imaging, we were able to detect preclinical abnormalities, distinguish characteristic changes common to ichthyosis, and reveal the depth and characteristics of corneal abnormalities. Therefore, patients with ichthyosis should be examined for DED and ectatic disorders early in clinical practice.

Partial Loss of Function ABCA12 Mutations Generate Reduced Deposition of Glucosyl-Ceramide, Leading to Patchy Ichthyosis and Erythrodermia Resembling Erythrokeratodermia Variabilis et Progressiva (EKVP)

Ichthyoses are genetically determined cornification disorders of the epidermis characterized by the presence of different degrees of scaling, hyperkeratosis, and erythroderma often associated with palmoplantar keratoderma. Different classifications of these diseases have been proposed, often based upon the involved genes and/or the clinical presentation. The clinical features of these diseases present some overlap of phenotypes among distinct genetic entities, depending mainly on the penetrance of mutations. In this study, using a clinical, genetic, and molecular approach, we analyzed a family with two affected members who had clinical and histological features resembling erythrokeratodermia variabilis (EKV) or a type of erythrodermic hyperkeratosis with palmoplantar keratoderma. Despite of the clinical presentation, we demonstrated that the affected patients were genetically double heterozygous for two different mutations in the ABCA12 gene, known to be responsible for harlequin ichthyosis. To explain the mild phenotype of our patients, we performed a molecular characterization of the skin. In the upper layers of the epidermis, the results showed a patchy presence of the glucosyl-ceramides (GlcCer), which is the lipid transported by ABCA12, fundamental in contributing to skin impermeability. Indeed, the two mutations detected do not completely abolish ABCA12 activity, indicating that the mild phenotype is due to a partial loss of function of the enzyme, thus giving rise to an intermediate phenotype resembling EKVP, due to a partial depletion of GlcCer deposition.

Clinical and genetic findings in 13 Chinese children with keratinopathic ichthyosis

Importance

Keratinopathic ichthyosis (KPI) represents a group of predominantly autosomal dominant genodermatoses resulting from mutations in the KRT1, KRT2, or KRT10 genes. In KPI, the relationship between genotype and phenotype is complex.

Objective

To analyze the clinical manifestations and gene mutations in Chinese patients with KPI.

Methods

Clinical data were collected from 13 children diagnosed with KPI, and peripheral blood DNA samples were extracted from both the patients and their parents Next-generation sequencing was performed using a congenital ichthyosis multi-gene panel, and the selected variants in the patients and their parents were further validated using the Sanger sequencing method.

Results

Genetic analysis identified missense mutations in either KRT1 or KRT10 in ten patients exhibiting varying degrees of severity and distinct features of epidermolytic ichthyosis. A missense hotspot mutation in KRT2 was identified in one patient with superficial epidermolytic ichthyosis. Additionally, two truncation mutations in KRT10 were detected, leading to the development of generalized ichthyosiform erythroderma. Ear malformation and ectropion at birth, scalp involvement, and palmoplantar hyperkeratosis were observed as early signs of ichthyosis with confetti.

Interpretation

We analyzed the genotype-phenotype correlations in KPI, revealing that the types and locations of different mutations are associated with distinct phenotypic characteristics. Oral acitretin could be considered a treatment option for severe patients at an appropriate dosage and timing.

Ichthyosis, cataracts, and motor delay in an infant: A case of Chanarin-Dorfman syndrome

Chanarin-Dorfman syndrome (CDS) is a rare, autosomal recessive disorder of impaired triacylglycerol catabolism leading to cytoplasmic deposition of triglycerides in various cell types. We describe the case of an 8-month-old boy with cataracts, strabismus, motor delays, and an ichthyosiform rash since birth. Genetic testing revealed a pathogenic variant of the ABHD5 gene, suggestive of CDS, and further workup demonstrated hepatic steatosis and myopathy. His ichthyosis improved with initiation of a diet low in very long-chain fatty acids and medium-chain fatty acid supplementation.

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.

Chronic activation of Toll-like receptor 2 induces an ichthyotic skin phenotype

BACKGROUND

Ichthyosis defines a group of chronic conditions that manifest phenotypically as a thick layer of scales, often affecting the entire skin. While the gene mutations that lead to ichthyosis are well documented, the actual signalling mechanisms that lead to scaling are poorly characterized; however, recent publications suggest that common mechanisms are active in ichthyotic tissue and in analogous models of ichthyosis.

OBJECTIVES

To determine common mechanisms of hyperkeratosis that may be easily targeted with small-molecule inhibitors.

METHODS

We combined gene expression analysis of gene-specific short hairpin RNA (shRNA) knockdowns in rat epidermal keratinocytes (REKs) of two genes mutated in autosomal recessive congenital ichthyosis (ARCI), Tgm1 and Alox12b, and proteomic analysis of skin scale from patients with ARCI, as well as RNA sequencing data from rat epidermal keratinocytes treated with the Toll-like receptor 2 (TLR2) agonist Pam3CSK4.

RESULTS

We identified common activation of the TLR2 pathway. Exogenous TLR2 activation led to increased expression of important cornified envelope genes and, in organotypic culture, caused hyperkeratosis. Conversely, blockade of TLR2 signalling in keratinocytes from patients with ichthyosis and our shRNA models reduced the expression of keratin 1, a structural protein overexpressed in ichthyosis scale. A time course of TLR2 activation in REKs revealed that although there was rapid initial activation of innate immune pathways, this was rapidly superseded by widespread upregulation of epidermal differentiation-related proteins. Both nuclear factor kappa B phosphorylation and GATA3 upregulation was associated with this switch, and GATA3 overexpression was sufficient to increase keratin 1 expression.

CONCLUSIONS

Taken together, these data define a dual role for TLR2 activation during epidermal barrier repair that may be a useful therapeutic modality in treating diseases of epidermal barrier dysfunction.

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.

Involvement of ω-O-acylceramides and protein-bound ceramides in oral permeability barrier formation

The permeability barrier present in the oral cavity is critical for protection from infection. Although lipids have properties suitable for permeability barrier formation, little is known about their role in oral barrier formation. Here, we show the presence of ω-O-acylceramides (acylceramides) and protein-bound ceramides, which are essential for the formation of permeability barriers in the epidermis, in the oral mucosae (buccal and tongue mucosae), esophagus, and stomach in mice. Conditional knockout of the fatty acid elongase Elovl1, which is involved in the synthesis of ≥C24 ceramides including acylceramides and protein-bound ceramides, in the oral mucosae and esophagus causes increased pigment penetration into the mucosal epithelium of the tongue and enhanced aversive responses to capsaicin-containing water. We find acylceramides in the buccal and gingival mucosae and protein-bound ceramides in the gingival mucosa in humans. These results indicate that acylceramides and protein-bound ceramides are important for oral permeability barrier formation.

Acral lamellar ichthyosis with amino acid substitution in the C-terminus of keratin 2

BACKGROUND

Most cases of hereditary ichthyoses present with generalized scaling and skin dryness. However, in some cases skin involvement is restricted to particular body regions as in acral lamellar ichthyosis.

OBJECTIVES

We report on the genetic basis of acral ichthyosis in two families presenting with a similar phenotype.

METHODS

Genetic testing was performed by targeted next generation sequencing and whole-exome sequencing. For identity-by-descent analysis, the parents were genotyped and data analysis was performed with the Chromosome Analysis Suite Software. RT-PCR with RNA extracted from skin samples was used to analyse the effect of variants on splicing.

RESULTS

Genetic testing identified a few heterozygous variants, but only the variant in KRT2 c.1912 T > C, p.Phe638Leu segregated with the disease and remained the strongest candidate. Pairwise identity-by-descent analysis revealed no indication of family relationship. Phenylalanine 638 is the second last amino acid upstream of the termination codon in the tail of K2, and substitution to leucine is predicted as probably damaging. Assessment of the variant is difficult, in part due to the lack of crystal structures of this region.

CONCLUSIONS

Altogether, we show that a type of autosomal dominant acral ichthyosis is most probably caused by an amino acid substitution in the C-terminus of keratin 2.

Interleukin-18 as a severity marker and novel potential therapeutic target for epidermolytic ichthyosis

BACKGROUND

Epidermolytic ichthyosis (EI) is a major form of nonsyndromic inherited ichthyosis, characterized by erythroderma, marked hyperkeratosis and scale, bulla and erosion at birth, associated with KRT1/KRT10 mutations. The cytokine and chemokine profiles in EI are poorly understood, and specific treatment options have not been established.

AIM

To explore novel biomarkers and therapeutic targets in patients with EI.

METHODS

We analysed cytokine levels in serum and skin samples from 10 patients with inherited ichthyosis, including seven patients with EI. Wild-type and mutant KRT1 constructs were established and transfected into HaCaT cells, an immortalized keratinocyte cell line, for in vitro immunoblotting and immunocytochemistry analyses.

RESULTS

Multiplex cytokine/chemokine analysis revealed that 10 cytokines/chemokines [interleukin (IL)-1β, IL-4, IL-17A, IL-16, IL-18, IL-1 receptor-α, macrophage colony-stimulating factor, interferon-α2, basic fibroblast growth factor and monocyte chemotactic protein-3] were significantly increased in patients with EI. Furthermore, IL-18 levels were significantly higher in patients with EI [n = 7; 2714.1 (1438.0) pg mL-1] than in healthy controls [n = 11; 218.4 (28.4) pg mL-1, P < 0.01]. Immunohistochemical analyses showed that IL-18 expression was elevated in skin samples from patients with EI. Serum IL-18 levels correlated with the severity of ichthyosis, as measured by the Ichthyosis Scoring System. Immunoblotting analysis revealed that mature IL-18 levels were increased in the supernatant of mutant KRT1 expressing HaCaT cells. Additionally, these cells showed NLRP3 aggregation in the cytoplasm and ASC clustered around mutant keratin aggregations. These findings suggest that mutant keratin might promote the activation of the NLRP3 inflammasome and its downstream caspase-1-mediated IL-18 release in keratinocytes from patients with EI.

CONCLUSIONS

Our results suggest that serum IL-18 is a severity marker released from the skin of patients with EI. Blockade of IL-18 may be a useful novel therapeutic option for patients with EI.