Evolution of genome diagnostics in epidermolysis bullosa: Unveiling the power of next-generation sequencing.

BACKGROUND: Genome diagnostics is considered gold standard diagnostics for epidermolysis bullosa (EB), a phenotypically and genetically heterogeneous group of rare disorders characterized by blistering and wounding of mucocutaneous tissues. EB is caused by pathogenic variants in genes encoding proteins of the dermo-epidermal junction. Accurate genetic diagnosis of EB is crucial for prognostication, counselling and precision-medicine. Genome diagnostics for EB started in 1991 with the introduction of Sanger sequencing (SS), analysing one gene at a time. In 2013, SS was superseded by next-generation sequencing (NGS), that allow for high-throughput sequencing of multiple genes in parallel. Several studies have shown a beneficial role for NGS in EB diagnostics, but its true benefit has not been quantified. OBJECTIVES: To determine the benefit of NGS in EB by systematically evaluating the performance of different genome diagnostics used over time based on robust data from the Dutch EB Registry. METHODS: The diagnostic performances of SS and NGS were systematically evaluated in a retrospective observational study including all index cases with a clinical diagnosis of EB in whom genome diagnostics was performed between 01 January 1994 and 01 January 2022 (n = 308), registered at the Dutch EB Expertise Centre. RESULTS: Over time, a genetic diagnosis was made in 289/308 (94%) EB cases. The diagnostic yield increased from 89% (SS) to 95% (NGS). Most importantly, NGS significantly reduced diagnostic turnaround time (39 days vs. 211 days, p < 0.001). The likelihood of detecting variants of uncertain significance and additional findings increased from 5% and 1% (SS) to 22% and 13% (NGS) respectively. CONCLUSIONS: Our study quantifies the benefit of NGS-based methods and demonstrate they have had a major impact on EB diagnostics through an increased diagnostic yield and a dramatically decreased turnaround time (39 days). Although our diagnostic yield is high (95%), further improvement of genome diagnostics is urgently needed to provide a genetic diagnosis in all EB patients.

Recessive mosaicism in ABCA12 causes blaschkoid congenital ichthyosiform erythroderma.

We report the unique case of a 3-year-old girl who presented with linear erythematosquamous lesions following the lines of Blaschko, suggestive of genetic mosaicism in the skin. Single-candidate gene analyses were performed on DNA from blood, excluding Conradi-Hünermann-Happle syndrome, erythrokeratodermia variabilis and a mosaic presentation of pityriasis rubra pilaris. With whole-exome sequencing (WES) on DNA from the patient's blood, a heterozygous missense mutation in exon 25 of the ABCA12 gene was detected. By manually scrutinizing the WES data, another low-percentage pathogenic frameshift mutation was found in the adjacent exon 26 of the same gene. This frameshift mutation was confirmed with Sanger sequencing in DNA isolated from a lesional skin biopsy. A subsequent cloning experiment was performed to prove that the patient is compound heterozygous for both mutations in the affected skin, explaining the blaschkoid ichthyosiform erythrodermic phenotype. The patient's phenotype was elucidated by the combination of a germline mutation and an acquired postzygotic mutation in ABCA12, resulting in the diagnosis of a mosaic manifestation of autosomal recessive congenital ichthyosis. Postzygotic compound allelic loss in autosomal recessive disorders is extremely rare and will not appear as the typical phenotype of the known germline mutation-associated disease. This is the first report of a proven biallelic mosaic presentation of an autosomal recessive genodermatosis, and we propose the term 'recessive mosaicism' for this kind of manifestation. What's already know about this topic? Specific mutations in the ABCA12 lipid transporter are known to cause different phenotypes like harlequin ichthyosis, congenital ichthyosiform erythroderma and lamellar ichthyosis. In mosaicism, two or more cell populations that are genetically different arise postzygotically in the developing embryo. In the skin, mosaicism can present itself in different patterns of affected skin, often caused by a dominant genetic mutation. What does this study add? We report a unique patient with blaschkoid congenital ichthyosiform erythroderma due to biallelic mutations, one inherited germline missense mutation and the other a postzygotic frameshift mutation in the ABCA12 gene. This study describes the diagnostic approach and applied research that can be used if one encounters a similar diagnostic dilemma with manifestations suspected for genetic mosaicism. We propose the term 'recessive mosaicism' for this kind of mosaic presentation of an autosomal recessive genodermatosis.

Genetic profiling of basal cell carcinomas detects postzygotic mosaicism in basal cell naevus syndrome.

Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene. Postzygotic mosaicism can also cause BCNS. Here we describe two patients, one with multiple basal cell carcinomas (BCCs) and one with clinical BCNS, who had no PTCH1 mutation in DNA extracted from blood. In both patients, we performed genetic analysis on different BCCs, revealing the presence of a shared PTCH1 mutation in all tumours. Our findings show that in patients with symptoms of BCNS and initial absence of a PTCH1 mutation in blood, genetic profiling of BCCs can detect postzygotic mosaicism. What's already known about this topic? Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene, but it can also be caused by low-grade postzygotic mosaicism in PTCH1. What does this study add? In patients suspected of having BCNS or patients with multiple basal cell carcinomas (BCCs) with a special distribution on the body and no mutation detected in blood, it is worthwhile to search for a shared PTCH1 mutation in their BCCs as this can detect postzygotic mosaicism. This information is important to ensure proper surveillance programmes, choose the right therapy and provide adequate genetic counselling.

Validation of the Simplified Psoriasis Index in Dutch children and adolescents with plaque psoriasis.

BACKGROUND: The Simplified Psoriasis Index (SPI) is a three-domain assessment measure for psoriasis, including separate indicators of current severity (SPI-s), psychosocial impact (SPI-p), and past history and interventions (SPI-i). There are two complementary versions available designed for completion by a health professional (proSPI) or by patient self-assessment (saSPI). The validity and reliability of the proSPI vs. saSPI have already been demonstrated in adults. To date, validated severity measures for paediatric psoriasis do not exist. OBJECTIVES: To validate the current severity (SPI-s) and psychosocial impact (SPI-p) domains of the proSPI and saSPI in children and adolescents with psoriasis. METHODS: All patients aged < 18 years with plaque psoriasis visiting the dermatology outpatient department of Radboud University Medical Center, the Netherlands, between September 2013 and April 2014 were asked to complete Dutch versions of the saSPI and the Children's Dermatology Life Quality Index (CDLQI). The original English versions of the proSPI and Psoriasis Area and Severity Index (PASI) were completed by the physician at the same visit. RESULTS: In total, 113 patients (median age 12·0 years, range 4-17) were included. There was a close correlation between the proSPI-s and PASI (r = 0·87), which was higher than between the saSPI-s and PASI (r = 0·69). The correlation between the SPI-p and CDLQI was 0·78. The full range of scores was utilized in both proSPI-s and SPI-p, although the highest saSPI-s score was 30 (maximum 50). CONCLUSIONS: In paediatric psoriasis, the proSPI and saSPI are shown to be valid and usable. The SPI-s and SPI-p can be readily introduced into routine clinical practice.

Postzygotic mosaicism in basal cell naevus syndrome.

Basal cell naevus syndrome (BCNS) is an autosomal dominant disorder most commonly caused by a germline mutation in the Drosophila homologue of patched-1 gene (PTCH1). Here we describe a patient with clinical signs of BCNS, caused by postzygotic mosaicism of a PTCH1 mutation. We performed restriction fragment length polymorphism analysis and Droplet Digital polymerase chain reaction to determine the degree of mosaicism in different tissues of this patient. Our case shows that a relatively low-grade mosaicism can lead to clinical signs reminiscent of those caused by a germline mutation. This finding has important implications for genetic counselling and therefore is pivotal to recognize for dermatologists, as well as for clinical geneticists and clinical laboratory geneticists.

Comparison of the Dermatology Life Quality Index and the Children's Dermatology Life Quality Index in assessment of quality of life in patients with psoriasis aged 16-17 years.

BACKGROUND: Dermatology Life Quality Index (DLQI) and Children's Dermatology Life Quality Index (CDLQI) are widely used to assess quality of life (QoL) in adults (≥ 16 years) and children (4-16 years) with psoriasis. In the age group 16-17 years, it is not known whether DLQI and CDLQI reflect QoL impairment in the same way. OBJECTIVES: To compare DLQI and CDLQI scores in patients with psoriasis aged 16-17 years. METHODS: Patients with psoriasis aged 16-17 years were asked to complete both the DLQI and CDLQI. RESULTS: Fifty-six patients were included. There was a high correlation between DLQI and CDLQI scores (r = 0·90, P < 0·001). The mean DLQI score (5·41 ± 5·20) was lower than the mean CDLQI (6·61 ± 5·74) (P < 0·001). The major part of this difference (∆0·61) was caused by the low score regarding sexual difficulties in the DLQI (0·11 ± 0·49) and the high score concerning sleep in the CDLQI (0·71 ± 0·93). In addition, the question related to sports scored 0·34 in the DLQI but 0·86 in the CDLQI (∆0·52). The question related to work/study in the DLQI scored lower than the question on school/holiday in the CDLQI (∆0·41). CONCLUSIONS: In patients with psoriasis aged 16-17 years, DLQI and CDLQI scores closely correlate, but the mean DLQI score was lower than the mean CDLQI score. This was caused primarily by differences in the answers to questions regarding sexual difficulties and sleep. As the QoL impacts experienced by people aged 16-17 may differ from those experienced by children or adults, QoL measures designed for use in this age range may have advantages over both child- and adult-specific measures.

Systemic treatments in paediatric psoriasis: a systematic evidence-based update.

In 2008, a systematic review revealed that evidence-based data on efficacy and safety of treatments in paediatric psoriasis are scarce and with low level of evidence. In recent years, publications on this topic have increased exponentially. To present a systematic, evidence-based update on the efficacy and safety of systemic treatments in paediatric psoriasis and to provide treatment recommendations, an update of the previous review was performed. PubMed, EMBASE and the Cochrane Controlled Clinical Trial Register were searched between January 2007 and March 2014 for all available literature on efficacy and safety of all systemic treatments in paediatric psoriasis. The levels of evidence were determined on the Oxford Centre for Evidence-based Medicine Levels of Evidence. The newly retrieved evidence was combined with the evidence available in the former review. Fifty-two studies were included: 36 from the former review, plus 16 new articles. New evidence on induction therapy was mainly available on fumaric acid esters (FAEs), which are shown to be effective in a subgroup of patients. Long-term (96 weeks) safety and efficacy data on etanercept were found. Prospective studies are scarce. Most conclusions are formulated on studies with low level of evidence. Of the conventional systemic treatments, methotrexate still has the most evidence albeit in a low number of patients and with a low level of evidence. FAEs seem to be effective in a subgroup of patients, with gastro-intestinal complaints, flushes and temporary shifts in leucocyte counts and liver enzymes being the main side-effects. Etanercept has still accumulated most evidence of the available systematic treatments, with a large efficacy and reassuring safety profile in a 96-week follow-up.

Are overweight and obese youths more often bullied by their peers? A meta-analysis on the correlation between weight status and bullying.

Research suggests that overweight and obese youths are stigmatized in contemporary society, and are more likely than normal-weight youths to become the victims of bullying. In the current study, meta-analyses were performed to analyze to what extent overweight and obese youths are more likely than normal-weight youths to be the victims of bullying. The databases Psychinfo, ERIC and Medline were searched for relevant articles. Retrieved articles were scanned to find further articles. Language was not used as an exclusion criterion. A total of 14 articles (N=55 231) were included in a meta-analysis on bullying and overweight youths, and a total of 16 articles (N=58 520) were included in a meta-analysis on bullying and obese youths. The results suggested that both overweight and obese youths were more likely to be victims of bullying. The results were not moderated by gender, overweight and obese boys and girls were equally likely to be victimized. Results remained significant after adjustment for publication bias. Both overweight and obesity are risk factors for being a victim of bullying.

Cutaneous clues for diagnosing X-chromosomal disorders.

In a multidisciplinary outpatient clinic for hereditary skin diseases and/or syndromes involving the skin, 7% (30 of 409) of patients were found to have an abnormality involving the X chromosome, a mutation in a gene located on the X chromosome or a clinical diagnosis of an X-linked monogenetic condition. The collaboration of a dermatologist and a clinical geneticist proves to be very valuable in recognizing and diagnosing these conditions. By combining their specific expertize in counselling an individual patient, X-linked diagnoses were recognized and could be confirmed by molecular and/or cytogenetic studies in 24 of 30 cases. Mosaicism plays an important role in many X-linked hereditary skin disorders. From our experience, we extracted clinical clues for specialists working in the field of genetics and/or dermatology for considering X-linked disorders involving the skin.

Calcipotriol/betamethasone dipropionate ointment in mild-to-moderate paediatric psoriasis: long-term daily clinical practice data in a prospective cohort.

BACKGROUND: Psoriasis in children has a significant negative impact on the quality of life (QoL) and effective treatment can improve this. The two-compound ointment calcipotriol 50 µg g(-1) and betamethasone dipropionate 0·5 mg g(-1) is an effective treatment option for moderate-to-severe psoriasis in adults. OBJECTIVES: To study prospectively the effectiveness and safety of calcipotriol/betamethasone dipropionate ointment in paediatric patients with mild-to-moderate plaque psoriasis in daily clinical practice and to investigate the influence on QoL. METHODS: Data were obtained from a prospective, longitudinal paediatric psoriasis registry, called Child-CAPTURE. Severity was assessed using the Psoriasis Area and Severity Index (PASI) and body surface area (BSA). The Children's Dermatology Life Quality Index (CDLQI) was used to assess QoL and visual analogue scores (VAS) for pain and itch were collected. For safety data the number of (serious) adverse events was recorded. RESULTS: Seventy-three patients (mean age 10·8 years, range 3-18) were treated for a median time of 35·0 weeks (range 1·0-176·0). At week 12, mean PASI decreased 15·4% (from 5·2 to 4·4), BSA barely changed, and median CDLQI decreased significantly from 5·5 to 4·0. VAS scores for pain and itch declined. At week 24, mean PASI decreased to 4·3 (17·3%). No related serious adverse events were observed. CONCLUSIONS: In this daily clinical practice study in paediatric psoriasis, calcipotriol/betamethasone dipropionate ointment initially improved mild-to-moderate psoriasis and then maintained its effect. In addition, it improved QoL, with few adverse events.

Variants in the L12 linker domain of KRT10 are causal to atypical epidermolytic ichthyosis.

Epidermolytic ichthyosis (EI) is a type of congenital ichthyosis, characterized by erythema and blistering at birth followed by hyperkeratosis. EI is caused by pathogenic variants in the genes KRT1 and KRT10, encoding the proteins keratin 1 (KRT1) and keratin 10 (KRT10), respectively, and is primarily transmitted by autosomal-dominant inheritance, although recessive inheritance caused by nonsense variants in KRT10 is also described. The keratins form a network of intermediate filaments and are a structural component of the cytoskeleton, giving strength and resilience to the skin. We present three cases of mild EI caused by pathogenic KRT10 variations in the L12 linker domain. To our knowledge, this is the first time L12 linker domain pathogenic variants are identified in KRT10 for EI. The aim of this study was to identify gene variants for patients with EI in KRT1 or KRT10. To establish the pathogenicity of the found variations in KRT10, we evaluated all patients and available family members clinically. Genetic analyses were performed using Sanger sequencing. Vectors containing wild-type or mutated forms of KRT10 were transfected into HaCaT cells and analyzed by high-resolution confocal microscopy. Genetic analysis of KRT10 identified a heterozygous de novo variant c.910G>A p.(Val304Met) in family 1, a familial heterozygous variant c.911T>C p.(Val304Ala) in family 2, and a familial heterozygous variant c.917T>C p.(Met306Thr) in family 3. All identified missense variants were located in the L12 linker domain of KRT10. In vitro study of aggregate formation of the missense variants in KRT10 only showed a very mild and not quantifiable aggregate formation in the KRT10 network, compared with the wild-type sequence. We report three different novel missense variants in the L12 linker domain of KRT10 in patients with an atypical, milder form of EI resembling peeling skin syndrome.

Keratolysis exfoliativa (dyshidrosis lamellosa sicca): a distinct peeling entity.

BACKGROUND: Keratolysis exfoliativa (KE), also known as dyshidrosis lamellosa sicca, is a palmoplantar dermatosis characterized by air-filled blisters and collarette desquamation. It has been regarded as a subtype of dyshidrotic eczema, a fungal infection or a dermatophytid reaction. KE may also resemble acral peeling skin syndrome and localized epidermolysis bullosa simplex. Although KE is a common disorder, it is a rarely reported and is an under-recognized dermatosis. OBJECTIVES: To delineate the characteristic features of KE. METHODS: We investigated the clinical, immunohistopathological, ultrastructural and molecular features of KE. Patients were included from the clinical records. Additional diagnostic research consisted of mutation analysis of the candidate genes TGM5, KRT5, KRT14, FLG, SPINK6 and SPINK9. RESULTS: A total of 24 patients with KE were identified, six with familial and 18 with sporadic KE. Lesions consisted of air-filled blisters only on palmoplantar skin, followed by collarette and lamellar peeling. Both light microscopy and electron microscopy showed cleavage and partially degraded corneodesmosomes within the stratum corneum, whereas immunofluorescence microscopy showed normal expression of corneodesmosomal components. No mutations were found in TGM5, KRT5/14 and SPINK6/9. There was no clear link with atopy or with FLG mutations. CONCLUSIONS: Our study suggests premature corneodesmolysis as the main pathological mechanism of this palmoplantar skin disorder. We conclude that KE appears to be a distinct peeling entity.

Extended haplotype studies in South African and Dutch variegate porphyria families carrying the recurrent p.R59W mutation confirm a common ancestry.

BACKGROUND: Variegate porphyria (VP) is due to a partial deficiency of protoporphyrinogen oxidase (PPOX), the seventh enzyme in the haem biosynthetic pathway. Clinically, VP is characterized by photosensitivity and acute neurovisceral attacks that can manifest separately or together in affected individuals. The disease is inherited in an autosomal dominant fashion with incomplete penetrance and PPOX gene mutations associated with VP are usually unique to patients and their families. In South Africa, however, VP is highly prevalent as the result of a founder mutation, designated p.R59W. Previous genealogical and haplotype studies showed a link between South African and Dutch carriers of p.R59W and it was suggested that this mutation was introduced to South Africa by Dutch settlers at the end of the 17th century. OBJECTIVES: To perform extended haplotype analysis in six South African and Dutch VP families with the p.R59W mutation. METHODS: Haplotyping of 13 microsatellite markers flanking the PPOX gene on chromosome 1q22-23 and five informative single nucleotide polymorphisms within and around the gene. RESULTS: A core haplotype cosegregated in all families studied. CONCLUSIONS: Our data deliver further confirmation that the South African and Dutch VP families carrying mutation p.R59W shared a common ancestor.

[Facial papules and pneumothoraces. Birt-Hogg-Dubé syndrome]. / Faziale Papeln und Pneumothoraces. Birt-Hogg-Dubé-Syndrom.

A 43-year-old man presented with white to skin-colored shiny papules on the face and neck. In addition, he had a positive family history and reported on multiple pneumothoraces. Histopathological examination revealed a papular mucinosis. Considering these findings, we made the diagnosis of Birt-Hogg-Dubé syndrome (BHDS) that was confirmed by molecular genetic analysis. This autosomal dominantly inherited tumor disorder is caused by germline mutations in the folliculin (FLCN) gene that encodes for the eponymous protein folliculin. Clinically, BHDS is predominantly characterized by the occurrence of fibrofolliculomas and trichodiscomas. A papular mucinosis, as encountered in our patient, has been described only once previously. Besides the cutaneous symptoms the disease can be associated with lung cysts and pneumothoraces as well as the development of benign and malignant kidney tumors. Following confirmation of BHDS on the DNA level, all patients with multiple cutaneous fibrofolliculomas should be treated in an interdisciplinary setting and undergo regular prophylactic screening examinations due to the association with renal cell carcinomas.