Unraveling the molecular mechanisms of cell migration impairment and apoptosis associated with steroid sulfatase deficiency: Implications for X-linked ichthyosis.

Steroid sulfatase (STS) deficiency is responsible for X-linked ichthyosis (XLI), a genetic disorder characterized by rough and dry skin caused by excessive keratinization. The impaired keratinization process leads to reduced cell mobility and increased apoptosis, which can cause an excessive buildup of the stratum corneum. In this study, we investigated the mechanisms underlying XLI and found that STS deficiency reduces cell mobility and increases apoptosis in human keratinocyte HaCaT cells. To explore these mechanisms further, RNA-sequencing was conducted on skin tissues from STS transgenic and knockout mice. Our RNA-seq results revealed that STS deficiency plays a critical role in regulating multiple signaling pathways associated with cell mobility and apoptosis, such as Wnt/ß signaling and the Hippo signaling pathway. Knockdown of the STS gene using shRNA in HaCaT cells led to an upregulation of E-cadherin expression and suppression of key factors involved in epithelial-mesenchymal transition (EMT), such as N-cadherin and vimentin. Inhibition of EMT involved the Hippo signaling pathway and reduction of HIF-1α. Interestingly, inhibiting STS with shRNA increased mitochondrial respiration levels, as demonstrated by the extracellular flux oxygen consumption rate. Additionally, we observed a significant increase in ROS production in partial STS knockout cells compared to control cells. Our study demonstrated that the excessive generation of ROS caused by STS deficiency induces the expression of Bax and Bak, leading to the release of cytochrome c and subsequent cell death. Consequently, STS deficiency impairs cell mobility and promotes apoptosis, offering insights into the pathophysiological processes and potential therapeutic targets for XLI.

STS and PUDP Deletion Identified by Targeted Panel Sequencing with CNV Analysis in X-Linked Ichthyosis: A Case Report and Literature Review.

X-linked recessive ichthyosis (XLI) is clinically characterized by dark brown, widespread dryness with polygonal scales. We describe the identification of STS and PUDP deletions using targeted panel sequencing combined with copy-number variation (CNV) analysis in XLI. A 9-month-old infant was admitted for genetic counseling. Since the second day after birth, the infant's skin tended to be dry and polygonal scales had accumulated over the abdomen and upper extremities. The infant's maternal uncle and brother (who had also exhibited similar skin symptoms from birth) presented with polygonal scales on their trunks. CNV analysis revealed a hemizygous deletion spanning 719.3 Kb on chromosome Xp22 (chrX:7,108,996-7,828,312), which included a segment of the STS gene and exhibited a Z ratio of -2 in the proband. Multiplex ligation-dependent probe amplification (MLPA) confirmed this interstitial Xp22.31 deletion. Our report underscores the importance of implementing CNV screening techniques, including sequencing data analysis and gene dosage assays such as MLPA, to detect substantial deletions that encompass the STS gene region of Xq22 in individuals suspected of having XLI.

Identification of a novel partial deletion of STS associated with pre-Descemet corneal dystrophy and X-linked ichthyosis.

Purpose: Pre-Descemet corneal dystrophy (PDCD) with X-linked ichthyosis (XLI) is associated with mutations in or deletions of the steroid sulfatase gene (STS). As only three cases of genetically confirmed PDCD associated with XLI have been reported, we sought to expand our understanding of the genetic basis of PDCD by screening STS in two previously unreported families. Materials and Methods: The affected individuals underwent cutaneous and slit-lamp examinations. Saliva samples collected from each affected individual served as a source of DNA for the amplification of the 10 coding exons of STS and flanking DNA markers. Results: The slit-lamp examination of three affected men (two of whom were brothers) from two families revealed bilateral punctate posterior corneal stromal opacities anterior to the Descemet membrane. Cutaneous examination demonstrated dry, coarse, scaly ichthyotic changes characteristic of XLI in all individuals. Genetic examination of the STS locus on the X chromosome in Case 1 revealed a deletion that spanned across DNA markers DXS1130-DXS237, which includes all the coding exons (exons 1-10) of STS. Genetic screening of Cases 2 and 3 revealed a partial deletion of the STS locus involving exons 1-7 and flanking DNA marker DXS1130 on the X chromosome. Conclusions: PDCD with XLI may be associated with either partial or complete deletion of STS. Despite the identification of point mutations, partial deletion, and complete deletion of STS in different affected families reported to date, there was no apparent difference in the affected phenotype between the families, suggesting that the identified variants likely all resulted in loss of function of steroid sulfatase.

Genetic Heterogeneity of X-Linked Ichthyosis in the Republic of North Ossetia-Alania, Case Series Report.

North Caucasus has always been a residence of a lot of different authentic ethnic groups speaking different languages and still living their traditional lifestyle. The diversity appeared to be reflected in the accumulation of different mutations causing common inherited disorders. X-linked ichthyosis represents the second most common form of genodermatoses after ichthyosis vulgaris. Eight patients from three unrelated families of different ethnic origin, Kumyk, Turkish Meskhetians, and Ossetian, with X-linked ichthyosis from the North Caucasian Republic of North Ossetia-Alania were examined. NGS technology was implied for searching for disease-causing variants in one of the index patients. Known pathogenic hemizygous deletion in the short arm of chromosome X encompassing the STS gene was defined in the Kumyk family. A further analysis allowed us to establish that likely the same deletion was a cause of ichthyosis in a family belonging to the Turkish Meskhetians ethnic group. In the Ossetian family, a likely pathogenic nucleotide substitution in the STS gene was defined; it segregated with the disease in the family. We molecularly confirmed XLI in eight patients from three examined families. Though in two families, Kumyk and Turkish Meskhetian, we revealed similar hemizygous deletions in the short arm of chromosome X, but their common origin was not likely. Forensic STR markers of the alleles carrying the deletion were defined to be different. However, here, common alleles haplotype is hard to track for a high local recombination rate. We supposed the deletion could arise as a de novo event in a recombination hot spot in the described and in other populations with a recurrent character. Defined here are the different molecular genetic causes of X-linked ichthyosis in families of different ethnic origins sharing the same residence place in the Republic of North Ossetia-Alania which could point to the existing reproductive barriers even inside close neighborhoods.

Phase IIb randomized CONTROL study demonstrates a novel topical isotretinoin formulation, TMB-001, is safe and effective in participants with either recessive X-linked or autosomal recessive lamellar congenital ichthyosis.

BACKGROUND: In two severe congenital ichthyosis subtypes, autosomal recessive lamellar ichthyosis (ARCI-LI) and X-linked recessive ichthyosis (XLRI), cutaneous manifestations include widespread scaling. Approved topical treatment options are limited to emollients and keratolytics. AIM: This analysis from the randomized phase IIb CONTROL study assessed whether the efficacy and safety of TMB-001, a novel topical isotretinoin ointment formulation, differed between ARCI-LI and XLRI subtypes. METHODS: Participants ≥ 9 years with genetically confirmed XLRI or ARCI-LI and ≥ 2 (of 4) Visual Index for Ichthyosis Severity (VIIS) assessment areas with ≥ 3 scaling score were randomized 1 : 1 : 1 to TMB-001 0.05%/TMB-001 0.1%/vehicle, twice daily for 12 weeks. The proportion of participants with ≥ 50% reduction vs. baseline in VIIS scaling (VIIS 50; primary endpoint) and ≥ 2-grade reduction in Investigator's Global Assessment (IGA)-scaling score vs. baseline (key secondary endpoint) were evaluated. Adverse events (AEs) were monitored. RESULTS: Among enrolled participants (TMB-001 0.05%, n = 11; 0.1%, n = 10; and vehicle, n = 12), 52% had ARCI-LI and 48% XLRI subtypes. Mean age was 33.6 and 35.4 years for participants with ARCI-LI and XLRI, respectively. Overall, 33%, 50% and 17% of participants with ARCI-LI and 100%, 33% and 75% of participants with XLRI achieved VIIS 50 in the TMB-001 0.05%, TMB-001 0.1% and vehicle groups, respectively (nominal P = 0.24 for 0.05% vs. vehicle, intent-to-treat population). Improvement of ≥ 2-grade IGA score was observed in 33%, 50% and 0% of participants with ARCI-LI and 83%, 33% and 25% of participants with XLRI in the TMB-001 0.05%, TMB-001 0.1% and vehicle groups, respectively (nominal P = 0.03 for 0.05% vs. vehicle, intention-to-treat population). Most AEs were application-site reactions. CONCLUSION: Regardless of congenital ichthyosis subtype, TMB-001 demonstrated greater proportions of participants achieving VIIS 50 and ≥ 2-grade IGA improvement vs. vehicle.

Characterising heart rhythm abnormalities associated with Xp22.31 deletion.

BACKGROUND: Genetic deletions at Xp22.31 are associated with the skin condition X linked ichthyosis (XLI), and with a substantially increased risk of atrial fibrillation/flutter (AF), in males. AF is associated with elevated thrombosis, heart failure, stroke and dementia risk. METHODS: Through: (a) examining deletion carriers with a diagnosis of AF in UK Biobank, (b) undertaking an online survey regarding abnormal heart rhythms (AHRs) in men/boys with XLI and female carriers of XLI-associated deletions and (c) screening for association between common genetic variants within Xp22.31 and idiopathic AF-related conditions in UK Biobank, we have investigated how AHRs manifest in deletion carriers, and have identified associated risk factors/comorbidities and candidate gene(s). Finally, we examined attitudes towards heart screening in deletion carriers. RESULTS: We show that AHRs may affect up to 35% of deletion carriers (compared with <20% of age-matched non-carriers), show no consistent pattern of onset but may be precipitated by stress, and typically resolve quickly and respond well to intervention. Gastrointestinal (GI) conditions and asthma/anaemia were the most strongly associated comorbidities in male and female deletion carriers with AHR, respectively. Genetic analysis indicated significant enrichment of common AF risk variants around STS (7 065 298-7 272 682 bp in GRCh37/hg19 genome build) in males, and of common GI disorder and asthma/anaemia risk variants around PNPLA4 (7 866 804-7 895 780 bp) in males and females, respectively. Deletion carriers were overwhelmingly in favour of cardiac screening implementation. CONCLUSION: Our data suggest AHRs are frequently associated with Xp22.31 deletion, and highlight subgroups of deletion carriers that may be prioritised for screening. Examining cardiac function further in deletion carriers, and in model systems lacking steroid sulfatase, may clarify AF pathophysiology.

X-linked recessive ichthyosis in 8 Tunisian patients: awareness of misdiagnosis due to the technical trap of the STS pseudogene.

INTRODUCTION: X-linked recessive ichthyosis (XLI) is a genodermatosis, caused by a deficiency of the steroid sulphatase enzyme encoded by the STS gene (OMIM # 300,747). Adopted XLI molecular diagnosis approaches differ from one laboratory to another depending on available technical facilities. Our work aims to figure out a sound diagnostic strategy for XLI. PATIENTS AND METHODS: We collected 8 patients with XLI, all males, from 3 unrelated Tunisian families from central Tunisia. Genetic diagnosis was conducted through a large panel of genetic techniques including: Sanger Sequencing, haplotype analysis of STR markers, MLPA analysis, FISH and array CGH. RESULTS: Direct Sanger sequencing of the STS gene showed the same deletion of 13 base pairs within the exon 4 in all patients resulting in a premature stop codon. However, all patients' mothers were not carriers of this variant and no common haplotype flanking STS gene was shared between affected patients. Sequence alignment with reference human genome revealed an unprocessed pseudogene of the STS gene located on the Y chromosome, on which the 13 bp deletion was actually located. STS MLPA analysis identified a deletion of the entire STS gene on X chromosome for all affected patients. This deletion was confirmed by FISH and delineated by array CGH. CONCLUSION: All our patients shared a deletion of the entire STS gene revealed by MLPA, confirmed by FISH and improved by array CGH. Geneticists must be aware of the presence of pseudogenes that can lead to XLI genetic misdiagnosis.

Mood symptoms, neurodevelopmental traits, and their contributory factors in X-linked ichthyosis, ichthyosis vulgaris and psoriasis.

BACKGROUND: High rates of adverse mood/neurodevelopmental traits are seen in multiple dermatological conditions, and can significantly affect patient quality of life. Understanding the sex-specific nature, magnitude, impact and basis of such traits in lesser-studied conditions like ichthyosis, is important for developing effective interventions. AIM: To quantify and compare relevant psychological traits in men with X-linked ichthyosis (XLI, n = 54) or in XLI carrier women (n = 83) and in patients with ichthyosis vulgaris (IV, men n = 23, women n = 59) or psoriasis (men n = 30, women n = 122), and to identify factors self-reported to contribute most towards depressive, anxious and irritable phenotypes. METHODS: Participants recruited via relevant charities or social media completed an online survey of established questionnaires. Data were analysed by sex and skin condition, and compared with general population data. RESULTS: Compared with the general population, there was a higher rate of lifetime prevalence of mood disorder diagnoses across all groups and of neurodevelopmental disorder diagnoses in the XLI groups. The groups exhibited similarly significant elevations in recent mood symptoms (Cohen d statistic 0.95-1.28, P < 0.001) and neurodevelopmental traits (d = 0.31-0.91, P < 0.05) compared with general population controls, and self-reported moderate effects on quality of life and stigmatization. There were strong positive associations between neurodevelopmental traits and recent mood symptoms (r > 0.47, P < 0.01), and between feelings of stigmatization and quality of life, particularly in men. Numerous factors were identified as contributing significantly to mood symptoms in a condition or sex-specific, or condition or sex-independent, manner. CONCLUSION: We found that individuals with XLI, IV or psoriasis show higher levels of mood disorder diagnoses and symptoms than matched general population controls, and that the prevalence and severity of these is similar across conditions. We also identified a number of factors potentially conferring either general or condition-specific risk of adverse mood symptoms in the three skin conditions, which could be targeted clinically and/or through education programmes. In clinical practice, recognizing mood/neurodevelopmental problems in ichthyosis and psoriasis, and addressing the predisposing factors identified by this study should benefit the mental health of affected individuals.

Steroid sulfatase deficiency causes cellular senescence and abnormal differentiation by inducing Yippee-like 3 expression in human keratinocytes.

Human steroid sulfatase (STS) is an enzyme that catalyzes the hydrolysis of dehydroepiandrosterone sulfate (DHEAS), estrone sulfate (E1S), and cholesterol sulfate. Abnormal expression of STS causes several diseases including colorectal, breast, and prostate cancer and refractory skin disease. In particular, accumulation of intracellular cholesterol sulfate by STS deficiency leads to a skin disorder with abnormal keratinization called X-linked ichthyosis (XLI). To determine the detailed mechanisms of XLI, we performed RNA sequencing (RNA-seq) analysis using human keratinocyte HaCaT cells treated with cholesterol and cholesterol sulfate. Of the genes with expression changes greater than 1.5-fold, Yippee-like 3 (YPEL3), a factor expected to affect cell differentiation, was found. Induction of YPEL3 causes permanent growth arrest, cellular senescence, and inhibition of metastasis in normal and tumor cells. In this study, we demonstrate that YPEL3 expression was induced by STS deficiency and, using the CRISPR/Cas9 system, a partial knock-out (STS+/-) cell line was constructed to establish a disease model for XLI studies. Furthermore, we show that increased expression of YPEL3 in STS-deficient cell lines promoted cellular senescence and expression of keratinization-related proteins such as involucrin and loricrin. Our results suggest that upregulation of YPEL3 expression by STS deficiency may play a crucial role in inducing cellular senescence and abnormal differentiation in human keratinocytes.

Types of congenital nonsyndromic ichthyoses.

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

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.

Medical and neurobehavioural phenotypes in male and female carriers of Xp22.31 duplications in the UK Biobank.

Deletions spanning the STS (steroid sulfatase) gene at Xp22.31 are associated with X-linked ichthyosis, corneal opacities, testicular maldescent, cardiac arrhythmia, and higher rates of developmental and mood disorders/traits, possibly related to the smaller volume of some basal ganglia structures. The consequences of duplication of the same genomic region have not been systematically assessed in large or adult samples, although evidence from case reports/series has indicated high rates of developmental phenotypes. We compared multiple measures of physical and mental health, cognition and neuroanatomy in male (n = 414) and female (n = 938) carriers of 0.8-2.5 Mb duplications spanning STS, and non-carrier male (n = 192, 826) and female (n = 227, 235) controls from the UK Biobank (recruited aged 40-69 from the UK general population). Clinical and self-reported diagnoses indicated a higher prevalence of inguinal hernia and mania/bipolar disorder respectively in male duplication carriers, and a higher prevalence of gastro-oesophageal reflux disease and blistering/desquamating skin disorder respectively in female duplication carriers; duplication carriers also exhibited reductions in several depression-related measures, and greater happiness. Cognitive function and academic achievement did not differ between comparison groups. Neuroanatomical analysis suggested greater lateral ventricle and putamen volume in duplication carriers. In conclusion, Xp22.31 duplications appear largely benign, but could slightly increase the likelihood of specific phenotypes (although results were only nominally-significant). In contrast to deletions, duplications might protect against depressive symptoms, possibly via higher STS expression/activity (resulting in elevated endogenous free steroid levels), and through contributing towards an enlarged putamen volume. These results should enable better genetic counselling of individuals with Xp22.31 microduplications.

Multimodal Imaging of Pre-Descemet Corneal Dystrophy Associated With X-Linked Ichthyosis and Deletion of the STS Gene.

PURPOSE: To investigate the presence of pre-Descemet corneal dystrophy (PDCD) in association with X-linked ichthyosis (XLI) in an 11-year-old boy using multimodal imaging and genetic analysis. METHODS: Corneal opacities were examined and imaged with slit-lamp biomicroscopy, anterior segment optical coherence tomography, noncontact specular microscopy, and in vivo confocal microscopy. Cytogenomic array analysis was performed using genomic DNA isolated from the patient. RESULTS: Corneal opacities characteristic of PDCD located in the posterior corneal stroma just anterior to Descemet membrane were identified by slit-lamp biomicroscopy. A pre-Descemet hyper-reflective line, consistent with these opacities, was seen with anterior segment optical coherence tomography. Scheimpflug tomography revealed a bimodal peak light scattering. In vivo confocal microscopy findings were unremarkable. Copy number analysis identified a 4389 kbp hemizygous deletion on the X chromosome (chr. X: 6,540,898-8,167,604), resulting in the deletion of 4 genes, including the known locus of XLI, the STS gene. CONCLUSIONS: This report demonstrates that PDCD-associated XLI may present in children and that the diagnosis may be confirmed through multimodal imaging in conjunction with genetic analysis.

Genetics of Inherited Ichthyoses and Related Diseases.

Inherited ichthyoses are classified as Mendelian disorders of cornification (MEDOC), which are defined on the basis of clinical and genetic features and are mainly divided into non-syndromic and syndromic ichthyoses. Numerous genes, which encode for corresponding proteins, are involved in the normal differentiation of keratinocytes (cornification) and participate in the formation of a functional epidermal barrier. To date, mutations in more than 50 genes are known to result in various types of ichthyoses. Thanks to modern genetic diagnostic methods based on targeted next generation sequencing (NGS), approximately 80-90% of cases can be resolved at present. Further sequencing methods covering the whole exome (WES) or whole genome (WGS) will obviously elucidate another portion of the remaining unknown ichthyoses in the future.

Medical and neurobehavioural phenotypes in carriers of X-linked ichthyosis-associated genetic deletions in the UK Biobank.

BACKGROUND: X-linked ichthyosis (XLI) is an uncommon dermatological condition resulting from a deficiency of the enzyme steroid sulfatase (STS), often caused by X-linked deletions spanning STS. Some medical comorbidities have been identified in XLI cases, but small samples of relatively young patients has limited this. STS is highly expressed in subcortical brain structures, and males with XLI and female deletion carriers appear at increased risk of developmental/mood disorders and associated traits; the neurocognitive basis of these findings has not been examined. METHODS: Using the UK Biobank resource, comprising participants aged 40-69 years recruited from the general UK population, we compared multiple medical/neurobehavioural phenotypes in males (n=86) and females (n=312) carrying genetic deletions spanning STS (0.8-2.5 Mb) (cases) to male (n=190 577) and female (n=227 862) non-carrier controls. RESULTS: We identified an elevated rate of atrial fibrillation/flutter in male deletion carriers (10.5% vs 2.7% in male controls, Benjamini-Hochberg corrected p=0.009), and increased rates of mental distress (p=0.003), irritability (p<0.001) and depressive-anxiety traits (p<0.05) in male deletion carriers relative to male controls completing the Mental Health Questionnaire. While academic attainment was unaffected, male and female deletion carriers exhibited impaired performance on the Fluid Intelligence Test (Cohen's d≤0.05, corrected p<0.1). Neuroanatomical analysis in female deletion carriers indicated reduced right putamen and left nucleus accumbens volumes (Cohen's d≤0.26, corrected p<0.1). CONCLUSION: Adult males with XLI disease-causing deletions are apparently at increased risk of cardiac arrhythmias and self-reported mood problems; altered basal ganglia structure may underlie altered function and XLI-associated psychiatric/behavioural phenotypes. These results provide information for genetic counselling of deletion-carrying individuals and reinforce the need for multidisciplinary medical care.

A novel nonsense mutation in the STS gene in a Pakistani family with X-linked recessive ichthyosis: including a very rare case of two homozygous female patients.

BACKGROUND: X-linked ichthyosis (XLI; OMIM# 308100) is a recessive keratinization disorder characterized by the presence of dark brown, polygonal, adherent scales on different parts of the body surface. It almost exclusively affects males and the estimated prevalence ranges from 1:2000-6000 in males worldwide. Extracutaneous manifestations are frequent including corneal opacities, cryptorchidism, neuropsychiatric symptoms or others. Up to 90% of XLI cases are caused by recurrent hemizygous microdeletion encompassing entire STS gene on chromosome Xp22.3, while only a minority of patients shows partial deletions or loss of function point mutations in STS. Larger deletions also involving contiguous genes are identified in syndromic patients. METHODS: Here, we report clinical and genetic findings of a large Pakistani family having 16 affected individuals including 2 females with XLI. Molecular karyotyping and direct DNA sequencing of coding region of the STS gene was performed. RESULTS: The clinical manifestations in affected individuals involved generalized dryness and scaling of the skin with polygonal, dark scales of the skin on scalp, trunk, limbs, and neck while sparing face, palms and soles. There were no associated extra-cutaneous features such as short stature, cryptorchidism, photophobia, corneal opacities, male baldness, and behavioral, cognitive, or neurological phenotypes including intellectual disability, autism or attention deficit hyperactivity disorder. Molecular karyotyping was normal and no copy number variation was found. Sanger sequencing identified a novel hemizygous nonsense mutation (c.287G > A; p.W96*), in exon 4 of STS gene in all affected male individuals. In addition, two XLI affected females in the family were found to be homozygous for the identified variant. CONCLUSIONS: This study is useful for understanding the genetic basis of XLI in the patients studied, for extending the known mutational spectrum of STS, diagnosis of female carriers and for further application of mutation screening in the genetic counseling of this family.

X-linked ichthyosis: Molecular findings in four pedigrees with inconspicuous clinical manifestations.

BACKGROUND: X-linked ichthyosis (XLI) is the second most common type of ichthyosis, which is characterized by wide and symmetric distribution of adherent, dry, and polygonal scales on the skin. Steroid sulfatase (STS) gene, which is located at chromosome Xp22.31, has been identified as the pathogenic gene of XLI. METHODS: In this study, chromosome karyotype analysis, bacterial artificial chromosomes-on-Beads™ (BoBs) assay, fluorescence in situ hybridization (FISH), and single nucleotide polymorphism array (SNP-array) were employed for the prenatal diagnoses in three pregnant women with high-risk serological screening results and a pregnant woman with mental retardation. RESULTS: STS deletion was identified at chromosome Xp22.31 in all four fetuses. Postnatal follow-up confirmed the diagnosis of ichthyosis in two male fetuses and revealed normal dermatological manifestations in other two female fetuses carrying ichthyosis. CONCLUSION: The results of the present study demonstrate that a combination of karyotypying, prenatal BoBs, FISH, and SNP-array may avoid the missed detection of common microdeletions and ensure the accuracy of the detection results, which provides a feasible tool for the reliable etiological diagnosis and better genetic counseling of XLI.