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 congenital ichthyosis due to novel CYP4F22 mutation presenting with a collodion membrane and ocular manifestations

Autosomal recessive congenital ichthyoses (ARCI) are a range of genetic disorders of keratinization. The rare CYP4F22 gene mutation can present with or without collodion membrane at birth and leads to the development of mild ichthyosis phenotype. We report a case of a novel pathogenic CYP4F22 genetic mutation presenting with collodion membrane and ocular manifestations. Ocular manifestations have recently been reported in a patient with ARCI with known CYP4F22 mutation, which further supports a possible correlation between the CYP4F22 mutation and this distinct phenotype.

Prenatal ultrasound detection of collodion membrane in association with an autosomal recessive congenital ichthyosis due to transglutaminase 1 deficiency

We describe a case of collodion baby diagnosed prenatally by ultrasound. Classic signs (ectropion, flattened nose, and eclabion) were detected on routine ultrasound at 21 weeks of gestation. At birth, the presence of collodion membrane was confirmed and subsequently, the diagnosis of an autosomal recessive congenital ichthyosis due to compound heterozygosity of the TGM1 gene was made.

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.

Case report of self-improving collodion ichthyosis in the newborn

Self-improving collodion ichthyosis (SICI) is a relatively rare subtype of autosomal recessive congenital ichthyosis (ARCI) that is often characterized by a collodion baby (CB) phenotype at birth. A newborn girl, just 1 hour old, presented with taut, shiny, thick yellow crusts, like parchment, and scales on her trunk and upper limbs. The tightening effect had caused both upper eyelids to appear everted, and her lips and auricles were deformed. Based on whole-exome sequencing and examination of the clinical phenotype, the patient was diagnosed with ARCI. After admission, the exposed mucosa was covered with a sterile Vaseline gauze dressing, and she was placed in an incubator set to a temperature of 32°C with a humidity level of 75%. One week later, the parchment-like scales had begun to flake off, and at the age of 3 weeks, all bodily skin appeared normal. SICI was diagnosed. After discharge, the patient was followed up to 3 months of age, at which time her growth and development were comparable to those of her peers. Clinicians should consider SICI as a possible diagnosis when analyzing the prognosis of patients with CB. Reducing water loss and maintaining the electrolyte balance are particularly important for SICI treatment.

Clinical and molecular characteristics of autosomal recessive congenital ichthyosis in Thailand

BACKGROUND

Autosomal recessive congenital ichthyosis (ARCI) is a heterogenous group of rare keratinization disorders. To date, more than 13 causative genes have been identified. However, data on clinical and molecular characteristics including genotype-phenotype correlation are lacking in Thailand.

OBJECTIVE

We collected cases diagnosed with non-syndromic ARCI and syndromic recessive congenital ichthyosis at the Institute of Dermatology from 2011 to 2021 and performed genetic testing with next-generation sequencing and assessed clinical details.

METHODS

Baseline demographic data, birth history, family history, skin manifestations at birth, current cutaneous manifestations, comorbidities, and response to treatments were assessed. DNA was screened for mutations using targeted gene sequencing of 45 genes related to congenital ichthyosis.

RESULTS

A total of 33 patients were analyzed with an average age of 23.8 ± 13.9 years. Congenital ichthyosiform erythroderma (CIE) was most common (60.6%), followed by lamellar ichthyosis (18.2%), self-improving congenital ichthyosis (6.1%), Netherton syndrome (6.1%), ichthyosis prematurity syndrome (3%), Sjögren-Larsson syndrome (3%) and bathing suit ichthyosis (3%). Eight genes were found with pathogenic variants in our cohort as follows: ABCA12 42.4% (14/33), NIPAL4 24.2% (8/33), TGM1 15.2% (5/33), SPINK5 6.1% (2/33), ALDH3A2 3% (1/33), SLC27A4 3% (1/33), CYP4F22 3% (1/33), and ST14 3% (1/33). Clinically, 79% of patients with ABCA12 pathogenic variants in this study had CIE, 79% of w had novel biallelic pathogenic compound heterozygous variants, whereas 21% had homozygous missense variants.

CONCLUSIONS

This is the first study to describe clinical and molecular findings of ARCI in a cohort from Thailand. Our findings demonstrate the clinical spectrum of the diseases and expand the molecular findings in a Southeast Asian population.

Novel Pathogenic Mutation of PNPLA1 Identified in Autosomal Recessive Congenital Ichthyosis: A Case Report

Autosomal recessive congenital ichthyosis (ARCI) is characterized by being born as collodion babies, hyperkeratosis, and skin scaling. We described a collodion baby at birth with mild ectropion, eclabium, and syndactyly. Whole exome sequencing showed a compound heterozygous variant c.[56C>A], p.(Ser19X) and c.[100G>A], p.(Ala34Thr) in the PNPLA1 gene [NM_001145717; exon 1]. The protein encoded by PNPLA1 acts as a unique transacylase that specifically transfers linoleic acid from triglyceride to ω-hydroxy fatty acid in ceramide, thus giving rise to ω-O-acylceramide, a particular class of sphingolipids that is essential for skin barrier function. The variant was located in the patatin core domain of PNPLA1 and resulted in a truncated protein which could disrupt the function of the protein. This case report highlights a novel compound heterozygous mutation in PNPLA1 identified in a Chinese child.

Ceramide Analysis in Combination With Genetic Testing May Provide a Precise Diagnosis for Self-Healing Collodion Babies

Self-healing collodion baby (SHCB), also called "self-improving collodion baby", is a rare mild variant of autosomal recessive congenital ichthyosis and is defined as a collodion baby who shows the nearly complete resolution of scaling within the first 3 months to 1 year of life. However, during the neonatal period, it is not easy to distinguish SHCB from other inflammatory forms of autosomal recessive congenital ichthyosis, such as congenital ichthyosiform erythroderma. Here, we report a case study of two Japanese SHCB patients with compound heterozygous mutations, c.235G>T (p.(Glu79∗))/ c.1189C>T (p.(Arg397Cys)) and c.1295A>G (p.(Tyr432Cys))/ c.1138delG (p.(Asp380Thrfs∗3)), in CYP4F22, which encodes cytochrome P450, family 4, subfamily F, polypeptide 22 (CYP4F22). Immunohistochemically, inflammation with the strong expression of IL-17C, IL-36γ, and TNF-α was seen in the skin at birth. CYP4F22 is an ultra-long-chain FA ω-hydroxylase responsible for ω-O-acylceramide (acylceramide) production. Among the epidermal ceramides, acylceramide is a key lipid in maintaining the epidermal permeability barrier function. We found that the levels of ceramides with ω-hydroxy FAs including acylceramides and the levels of protein-bound ceramides were much lower in stratum corneum samples obtained by tape stripping from SHCB patients than in those from their unaffected parents and individuals without SHCB. Additionally, our cell-based enzyme assay revealed that two mutants, p.(Glu79∗) and p.(Arg397Cys), had no enzyme activity. Our findings suggest that genetic testing coupled with noninvasive ceramide analyses using tape-stripped stratum corneum samples might be useful for the early and precise diagnosis of congenital ichthyoses, including SHCB.

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.

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

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

The Burden of Autosomal Recessive Congenital Ichthyoses on Patients and their Families: An Italian Multicentre Study

Autosomal recessive congenital ichthyoses (ARCI) are characterized by generalized skin scaling, hyperkeratosis, erythroderma, and disabling features affecting the skin (palmoplantar keratoderma, fissures, pain, itch), eyes, ears, and joints. Disease severity and chronicity, patient disfigurement, and time and costs required for care impose a major burden on quality of life. This multicentre cross-sectional study investigated the impact of ARCI on quality of life of patients and families, using the Dermatology Life Quality Index (DLQI), the Children DLQI (CDLQI) and Family Burden of Ichthyosis (FBI) questionnaires. Disease severity was assessed by a dermatologist. A total of 94 patients were recruited, of whom 52 (55.3%) children. Mean age was 20.1 (median 13.5) years. The mean CDLQI/DLQI score was 7.8, and 21 patients scored >10, indicating a major impairment in quality of life: symptoms, feelings and treatment problems were the most affected domains of quality of life. FBI showed a major repercussion on psychological factors and work. The results of this study highlight the impact of ARCI on specific aspects of patient and family life, underlining the need for psychological support.

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.

hiPSC-Derived Epidermal Keratinocytes from Ichthyosis Patients Show Altered Expression of Cornification Markers

Inherited ichthyoses represent a large heterogeneous group of skin disorders characterised by impaired epidermal barrier function and disturbed cornification. Current knowledge about disease mechanisms has been uncovered mainly through the use of mouse models or human skin organotypic models. However, most mouse lines suffer from severe epidermal barrier defects causing neonatal death and human keratinocytes have very limited proliferation ability in vitro. Therefore, the development of disease models based on patient derived human induced pluripotent stem cells (hiPSCs) is highly relevant. For this purpose, we have generated hiPSCs from patients with congenital ichthyosis, either non-syndromic autosomal recessive congenital ichthyosis (ARCI) or the ichthyosis syndrome trichothiodystrophy (TTD). hiPSCs were successfully differentiated into basal keratinocyte-like cells (hiPSC-bKs), with high expression of epidermal keratins. In the presence of higher calcium concentrations, terminal differentiation of hiPSC-bKs was induced and markers KRT1 and IVL expressed. TTD1 hiPSC-bKs showed reduced expression of FLG, SPRR2B and lipoxygenase genes. ARCI hiPSC-bKs showed more severe defects, with downregulation of several cornification genes. The application of hiPSC technology to TTD1 and ARCI demonstrates the successful generation of in vitro models mimicking the disease phenotypes, proving a valuable system both for further molecular investigations and drug development for ichthyosis patients.

Autosomal Recessive Congenital Ichthyosis and Steroid-Resistant Nephrotic Syndrome due to Homozygous Mutation in the ALOX12B gene: A Novel Association with Review of Literature

Nephrotic syndrome (NS) associated with autosomal recessive congenital ichthyosis (ARCI) is a rare association. In this article, we described a 4-year-old boy with steroid-resistant NS (SRNS) who had a history of ichthyotic skin lesions since birth. Renal biopsy revealed focal segmental glomerulosclerosis (tip variant). The skin biopsy was consistent with the findings of ichthyosis. Next-generation sequencing revealed a homozygous pathogenic variant (c.1625_1626del) in the exon 12 of the ALOX12B gene, confirming the diagnosis of ARCI2. The ALOX12B gene belongs to the lipoxygenase family and has a pivotal role in the formation of lipid layers in the epidermis. Leukotrienes have a counter-regulatory effect within the inflamed glomeruli, which influences the vascular tone and glomerular basement membrane permeability, that can be implicated in the pathogenesis of the NS. This child is currently in remission, on tacrolimus and low-dose prednisolone, with emollients and is on regular follow-up. SRNS associated with congenital ichthyosis secondary to a mutation in the ALOX12B gene has never been reported so far. The knowledge regarding this novel association will help the treating physicians in diagnosing this condition early, which will enable proper genetic counseling and prognostication of the disease to the family.

Phenotypic suppression of acral peeling skin syndrome in a patient with autosomal recessive congenital ichthyosis

Autosomal recessive congenital ichthyosis (ARCI) manifests with generalized scaling often associated with generalized erythema. Mutations in at least 13 different genes have been reported to cause ARCI. Acral peeling skin syndrome (APSS) is a rare autosomal recessive disorder manifesting with peeling over the distal limbs and dorsal surfaces of hands and feet. APSS is mostly due to mutations in TGM5, encoding transglutaminase 5. Both ARCI and APSS are fully penetrant genetic traits. Here, we describe a consanguineous family in which one patient with mild ARCI was found to carry a homozygous mutation in ALOXE3 (c.1238G > A; p.Gly413Asp). The patient was also found to carry a known pathogenic homozygous mutation in TGM5 (c.1335G > C; p.Lys445Asn) but did not display acral peeling skin. Her uncle carried the same homozygous mutation in TGM5 but carried the ALOXE3 mutation in a heterozygous state and showed clinical features typical of APSS. Taken collectively, these observations suggested that the ALOXE3 mutation suppresses the clinical expression of the TGM5 variant. We hypothesized that ALOXE3 deficiency may affect the expression of a protein capable of compensating for the lack of TGM5 expression. Downregulation of ALOXE3 in primary human keratinocytes resulted in increased levels of corneodesmosin, which plays a critical role in the maintenance of cell-cell adhesion in the upper epidermal layers. Accordingly, ectopic corneodesmosin expression rescued the cell-cell adhesion defect caused by TGM5 deficiency in keratinocytes as ascertained by the dispase dissociation assay. The present data thus provide evidence for phenotypic suppression in a human hereditary skin disorder.

A case of self-improving collodion ichthyosis in Vietnam

Autosomal recessive congenital ichthyosis is a heterogeneous group of congenital disorders characterized by aberrant skin cornification and diffuse skin scaling. Some patients with this condition are born encased in a collodion membrane which is later shed, revealing the underlying skin disorder. Self-healing collodion baby (SHCB) is a less common phenotype of this disorder, accounting for about 10% of the patients, in which the membrane peels after several weeks, leaving no underlying skin aberration. Here, we report and discuss the diagnosis and management of an infant with SHCB in Vietnam due to compound heterozygous pathogenic mutations in TGM1.

Molecular Genetics of Keratinization Disorders - What's New About Ichthyosis

The heritable forms of keratinization disorders, including various forms of ichthyosis and keratodermas, comprise a phenotypically heterogeneous group of diseases which can be divided into syndromic and non-syndromic forms. In the non-syndromic forms, the clinical manifestations are limited to the cutaneous structures while the syndromic ones are associated with a spectrum of extracutaneous manifestations. The inheritance in different families can be autosomal dominant, autosomal recessive or either X-linked dominant or recessive. Currently at least 67 distinct genes have been associated with different forms of ichthyosis. These genes can be grouped on the basis of their physiological involvement, including genes encoding structural components of epidermis, those involved in epidermal lipid metabolism, or those critical for cell-cell adhesion, and keratinocyte differentiation. This overview highlights some of the recent progress made in understanding the molecular genetics of keratinization disorders, and presents selected, recently characterized cases as representative of different forms of heritable ichthyosis.

Identification and association of recurrent ALOXE3 mutation with non-bullous congenital ichthyosiform erythroderma in two ethnically distinct Pakistani families

Non-bullous congenital ichthyosiform erythroderma (NCIE) is characterized by skin scaling with erythema. In this study, two Pakistani families with NCIE are genetically characterized through Whole Exome and Sanger sequencing to identify molecular basis of the disease. We identified a nonsense homozygous c.2026C>T mutation of ALOXE3, causing premature termination of the eLOX3 protein (p.Q676X). In silico studies predicted impaired enzymatic activity of the premature truncated eLOX3, leading to abnormal synthesis of specific hepoxilin derivatives, essential for epidermal barrier formation. It is the first ever study reporting homozygotes of p.Q676X mutation in ethnically distinct two Pakistani families; otherwise, heterozygotes of the said mutation have been reported in South Asian population only. Hence, mutation seems to be region-specific and may be useful for molecular diagnosis of NCIE. Moreover, our findings should help in genetic counseling and career screening.

Results of a nationwide epidemiologic survey of autosomal recessive congenital ichthyosis and ichthyosis syndromes in Japan

BACKGROUND

Autosomal recessive congenital ichthyosis (ARCI) and ichthyosis syndrome (IS) are rare genetic skin disorders.

OBJECTIVE

To estimate the number of patients with ARCI and IS in Japan and clarify the clinicoepidemiologic features of these diseases.

METHODS

We performed a nationwide survey of patients treated for ARCI or IS during January 2005-December 2009. We developed diagnostic criteria and conducted a primary survey in a stratified random sample of Japanese hospitals to quantify the number of outpatients and inpatients with ARCI or IS. We performed a secondary survey of clinicoepidemiologic features in positive cases.

RESULTS

The estimated number of patients receiving treatment for ARCI and IS during 2005-2009 was 220 (95% confidence interval [CI] 180-260). The estimated disease distribution was as follows: 95 (95% CI 80-110) patients with nonbullous congenital ichthyosiform erythroderma, 30 (95% CI 20-40) with lamellar ichthyosis, 15 (95% CI 10-20) with harlequin ichthyosis, and 85 (95% CI 50-120) with IS.

LIMITATIONS

Patients with a mild case of the disease might not have visited a dermatology department, potentially causing underestimation of affected patients.

CONCLUSION

We report the estimated number of patients with ARCI and IS in Japan and sex differences in the age distribution.

An IL-17-dominant immune profile is shared across the major orphan forms of ichthyosis

BACKGROUND

The ichthyoses are rare genetic disorders associated with generalized scaling, erythema, and epidermal barrier impairment. Pathogenesis-based therapy is largely lacking because the underlying molecular basis is poorly understood.

OBJECTIVE

We sought to characterize molecularly cutaneous inflammation and its correlation with clinical and barrier characteristics.

METHODS

We analyzed biopsy specimens from 21 genotyped patients with ichthyosis (congenital ichthyosiform erythroderma, n = 6; lamellar ichthyosis, n = 7; epidermolytic ichthyosis, n = 5; and Netherton syndrome, n = 3) using immunohistochemistry and RT-PCR and compared them with specimens from healthy control subjects, patients with atopic dermatitis (AD), and patients with psoriasis. Clinical measures included the Ichthyosis Area Severity Index (IASI), which integrates erythema (IASI-E) and scaling (IASI-S); transepidermal water loss; and pruritus.

RESULTS

Ichthyosis samples showed increased epidermal hyperplasia (increased thickness and keratin 16 expression) and T-cell and dendritic cell infiltrates. Increases of general inflammatory (IL-2), innate (IL-1β), and some T_H1/interferon (IFN-γ) markers in patients with ichthyosis were comparable with those in patients with psoriasis or AD. TNF-α levels in patients with ichthyosis were increased only in those with Netherton syndrome but were much lower than in patients with psoriasis and those with AD. Expression of T_H2 cytokines (IL-13 and IL-31) was similar to that seen in control subjects. The striking induction of IL-17-related genes or markers synergistically induced by IL-17 and TNF-α (IL-17A/C, IL-19, CXCL1, PI3, CCL20, and IL36G; P < .05) in patients with ichthyosis was similar to that seen in patients with psoriasis. IASI and IASI-E scores strongly correlated with IL-17A (r = 0.74, P < .001) and IL-17/TNF-synergistic/additive gene expression. These markers also significantly correlated with transepidermal water loss, suggesting a link between the barrier defect and inflammation in patients with ichthyosis.

CONCLUSION

Our data associate a shared T_H17/IL-23 immune fingerprint with the major orphan forms of ichthyosis and raise the possibility of IL-17-targeting strategies.

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.

A systematic review of clinical trials of treatments for the congenital ichthyoses, excluding ichthyosis vulgaris

BACKGROUND

The ichthyoses comprise a group of inherited disorders of keratinization. Because of the need for lifelong treatment, it is important that therapies are beneficial, safe, and well tolerated.

OBJECTIVES

We sought to review the evidence on existing treatments for the congenital ichthyoses, excluding ichthyosis vulgaris.

METHOD

We undertook a systematic review using the methodology of the Cochrane Collaboration. Articles published in MEDLINE, EMBASE, and CENTRAL and registered clinical trials were screened. Randomized controlled trials involving patients with the inherited ichthyoses, either syndromic or nonsyndromic but excluding ichthyosis vulgaris, were considered.

RESULTS

Six trials met the inclusion criteria. Topical treatments including 5% urea, 20% propylene glycol alone or in combination with 5% lactic acid, calcipotriol ointment, and liarozole 5% cream showed therapeutic benefit. Oral liarozole, a retinoic acid metabolism blocking agent, showed no advantage over oral acitretin.

LIMITATIONS

Most studies were performed on a small sample of patients and lacked methodological and reporting quality. The small number of trials and the nearly constant positive results make publication bias likely. The absence of standardization of outcome measures precluded the comparison of studies.

CONCLUSIONS

Topical treatments including emollients, calcipotriol ointment, and liarozole cream seem to have therapeutic benefit and a good safety profile, although the use of topical calcipotriol is limited by a maximum weekly dose of 100 g. The advantage of oral liarozole over acitretin is uncertain. Multicenter trials comparing oral and topical interventions and evaluation of long-term outcomes are needed.