Exacerbation of ichthyosis vulgaris phenotype by co-inheritance of STS and FLG mutations in a Chinese family with ichthyosis: a case report

Maternal Xp22.31 copy-number variations detected in non-invasive prenatal screening effectively guide the prenatal diagnosis of X-linked ichthyosis

Background and aims: X-linked ichthyosis (XLI) is a common recessive genetic disease caused by the deletion of steroid sulfatase (STS) in Xp22.31. Maternal copy-number deletions in Xp22.31 (covering STS) can be considered an incidental benefit of genome-wide cell-free DNA profiling. Here, we explored the accuracy and clinical value of maternal deletions in Xp22.31 during non-invasive prenatal screening (NIPS).

Materials and methods: We evaluated 13,156 pregnant women who completed NIPS. The maternal deletions in Xp22.31 revealed by NIPS were confirmed with maternal white blood cells by chromosome microarray analysis (CMA) or copy-number variation sequencing (CNV-seq). Suspected positive women pregnant with male fetuses were informed and provided with prenatal genetic counseling.

Results: Nineteen maternal deletions in Xp22.31 covering STS were detected by NIPS, which were all confirmed, ranging in size from 0.61 to 1.77 Mb. Among them, eleven women with deletions in male fetuses accepted prenatal diagnoses, and finally nine cases of XLI were diagnosed. The nine XLI males had differing degrees of skin abnormalities, and of them, some male members of ten families had symptoms associated with XLI.

Conclusion: NIPS has the potential to detect clinically significant maternal X chromosomal CNVs causing XLI, which can guide the prenatal diagnosis of X-linked ichthyosis and reflect the family history, so as to enhance pregnancy management as well as children and family members’ health management.

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.

A Narrative Review on the Role of Acids, Steroids, and Kinase Inhibitors in the Treatment of Keratosis Pilaris

Keratosis pilaris is a common and benign genetic skin disorder that results in patches of rough bumps on the skin, with varying degrees of reddening and inflammation. These bumps in the skin are caused by the dead skin cells that plug the hair follicles. Keratosis pilaris often manifests in small, hard bumps on the legs and arms. A common treatment method for many acne conditions, including keratosis pilaris, is acid, which has shown promise in recent years. This review examines the use and success of multiple types of acids, steroids, and kinase inhibitors in clinical and non-clinical settings to treat and understand keratosis pilaris. In the treatment of keratosis pilaris, acid primarily works by breaking down the dead skin cells that clog the hair follicles. Some types of steroids have anti-inflammatory properties that have proven useful in minimizing the appearance of acne. Kinase inhibitors control important skin cell functions, such as cell signaling, metabolism, division, and survival, which undoubtedly affect the appearance of skin as a whole. The known impact of acid, steroids, and kinase inhibitors on keratosis pilaris is underestimated and should be given more attention by healthcare industry leaders.

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 unique case of a digital tourniquet in ichthyosis vulgaris

We report a unique case of a digital tourniquet in a patient with ichthyosis vulgaris. We have identified no previous case reports documenting the occurrence of a digital tourniquet in patients caused by this condition. Ichthyosis vulgaris is a skin condition which causes increased scaling of the skin and in this case, resulted in the formation of a tourniquet-like circumferential constriction to one of the patient's digits.

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.