A multistep approach to the diagnosis of rare genodermatoses

Genetics for dermatologists. Part 2: Clinical evaluation, sequencing technologies and interpretation

Genomic sequencing technologies have revolutionised the diagnostic approach to genodermatoses, facilitating precise diagnosis, offering unparalleled insights into pathogenesis, and guiding personalised treatment strategies. In this article, we provide an outline for clinical evaluation, how to choose the most suitable genetic test for different dermatological presentations and examine indications for single-gene tests, gene panels, whole exome, and whole genome sequencing. We then delve into sequencing technologies, including next-generation sequencing (NGS) and its various platforms, detailing their strengths, limitations, and clinical applications. By understanding these technologies, clinicians will be better equipped to interpret test results accurately and collaborate with genetic counsellors and laboratory experts effectively.

Molecular insights into genodermatoses: Genetic findings from 43 patients

Genodermatoses, a group of inherited skin disorders, are characterized by significant genetic heterogeneity and clinical variability, often posing diagnostic and therapeutic challenges. Advances in next-generation sequencing (NGS) technologies, such as whole exome sequencing (WES) and clinical exome sequencing (CES), have transformed the diagnostic landscape by enabling comprehensive genetic analysis. This study aimed to investigate the molecular spectrum and clinical relevance of genetic findings in 43 patients diagnosed with genodermatoses. Demographic, clinical, and molecular data were collected, and genetic testing was performed using the MGI-Seq platform. Variants were analyzed for pathogenicity, zygosity, and novelty. Neurofibromatosis Type 1 (27.9%) and Epidermolysis Bullosa (23.2%) were the most common diagnoses, followed by Ichthyosis (16.2%) and Oculocutaneous Albinism (13.9%). Less frequent conditions included Ectodermal Dysplasia (6.9%) and single cases of Palmoplantar Keratoderma, PTEN Hamartoma Syndrome, Rothmund-Thomson Syndrome, Xeroderma Pigmentosum, and Megaconial Congenital Muscular Dystrophy (each 2.3%). Molecular findings underscored the genetic complexity of genodermatoses, with 42 distinct variants identified across 19 genes. Of these, 13 variants (31%) were novel, expanding the known molecular spectrum. The novel variants were detected in genes including NF1, COL7A1, ITGB4, COL17A1, NIPAL4, ALOX12B, KRT10, ST14, OCA2, and PTEN, highlighting the diagnostic value of comprehensive genetic analysis. The mean age at diagnosis varied significantly among conditions, reflecting the diagnostic challenges and clinical variability of genodermatoses. This study emphasizes the critical role of WES and CES in diagnosing genodermatoses and understanding their molecular basis, which enhances diagnostic accuracy and supports personalized management strategies.

Getting it right the first time: an Irish paediatric dermatology perspective from a national care centre

The Dermatology: 'Getting It Right the First Time' (GIRFT) Programme National Specialty Report recommended improving access to, and the quality of, paediatric dermatology services. Understanding referral patterns makes it easier to identify areas that can be improved. This study analysed 292 new referrals to a national care centre that provides secondary care to 50% of all Irish children. Results showed that 51% of new referrals could have been managed in primary care and 41% of new referrals were inappropriate, including 5.5% having no abnormal skin findings. These results indicate that up to 876 referrals could have been avoided over a 13-month period, freeing up resources and reducing wait times for cases more appropriate for a secondary and tertiary care centre. This would improve access for children, allowing them to be diagnosed at the right place and time, in alignment with GIRFT values.

Dermoscopic Patterns of Genodermatoses: A Comprehensive Analysis

(1) Background: Genodermatoses are a clinically and genetically heterogenous group of inherited skin disorders. Diagnosing inherited skin diseases is a challenging task due to their rarity and diversity. Dermoscopy is a non-invasive, easily accessible, and rapid tool used in dermatology not only for diagnostic processes but also for monitoring therapeutic responses. Standardized terminologies have been published for its proper use, reproducibility, and comparability of dermoscopic terms. (2) Methods: Here, we aimed to investigate dermoscopic features in various genodermatoses by conducting a systematic review and comparing its results to our own findings, data of patients diagnosed with genodermatoses at the Department of Dermatology, Venereology and Dermatooncology, Semmelweis University. (3) Results: Our systematic search provided a total of 471 articles, of which 83 reported both descriptive and metaphoric dermoscopic terminologies of 14 genodermatoses. The literature data were then compared to the data of 119 patients with 14 genodermatoses diagnosed in our department. (4) Conclusion: Dermoscopy is a valuable tool in the diagnosis of genodermatoses, especially when symptoms are mild. To enable the use of dermoscopy as an auxiliary diagnostic method, existing standardized terminologies should be extended to more genodermatoses.

Clinical and molecular diagnosis of genodermatoses: Review and perspectives

Genodermatoses are a complex and heterogeneous group of genetic skin disorders characterized by variable expression and clinical and genetic heterogeneity, rendering their diagnosis challenging. DNA-based techniques, like whole-exome sequencing, can establish a diagnosis in 50% of cases. RNA-sequencing is emerging as an attractive tool that can obtain information regarding gene expression while integrating functional genomic data with regard to the interpretation of variants. This increases the diagnostic rate by an additional 10-15%. In the present review, we detail the clinical steps involved in the diagnosis of genodermatoses, as well as the current DNA-based technologies available to clinicians. Herein, the intention is to facilitate a better understanding of the possibilities and limitations of these diagnostic technologies. In addition, this review could guide dermatologists through new emerging techniques, such as RNA-sequencing and its applications to familiarizing them with future techniques. Currently, this multi-omics approach is likely the best strategy designed to promote the diagnosis of patients with genodermatoses and discover new skin disease genes that could result in novel targeted therapies.

Das NF1-Mikrodeletions-Syndrom: Die frühzeitige genetische Diagnose erleichtert den Umgang mit einer klinisch definierten Erkrankung

Neurofibromatose Typ-1 (NF1) ist ein Genodermatose, die häufig in der Dermatologie behandelt wird. Bei vielen Patienten mit NF1 wird die Diagnose aufgrund klinischer Merkmale erstellt wie Café-au-Lait-Flecken, Freckling und plexiformen Neurofibromen, die schon während der frühen Kindheit auftreten können. Später im Leben sind oft kutane Neurofibrome weitere wichtige diagnostische Merkmale. Die NF1 ist durch ausgeprägte klinische Variabilität und eine breite Heterogenität der NF1-Genmutationen charakterisiert, was Genotyp/Phänotyp-Korrelationen erschwert. Wichtige Ausnahmen sind NF1-Mikrodeletionen, die bei 5-11 % aller NF1-Patienten auftreten. Patienten mit NF1-Mikrodeletionen zeigen häufig spezifische Merkmale wie Gesichtsdysmorphien und sind von großer Statur. Zudem sind früh auftretende kutane und subkutane Neurofibrome, schwere Entwicklungsverzögerungen in multiplen Bereichen sowie kognitive Einschränkungen pathognomonisch für das NF1-Mikrodeletions-Syndrom. Darüber hinaus sind NF1-Mikrodeletionen mit einem Risiko für maligne periphere Nervenscheidentumoren assoziiert, das etwa zweifach höher ist als bei intragenischen NF1-Mutationen. Die schweren klinischen Manifestationen bei Patienten mit NF1-Mikrodeletionen machen eine frühe multidisziplinäre klinische Betreuung und häufige Tumor-Überwachung der Patienten notwendig. Wenn bei einem Patienten Red-Flag-Symptome für das NF1-Mikrodeletions-Syndrom auftreten, ist eine frühzeitige genetische Untersuchung notwendig, um eine NF1-Mikrodeletion zu bestätigen oder auszuschließen.

The NF1 microdeletion syndrome: early genetic diagnosis facilitates the management of a clinically defined disease

Neurofibromatosis type-1 (NF1) is a genodermatosis frequently encountered in general dermatology. In many patients, the diagnosis of NF1 is made clinically based on the presence of café-au-lait macules and skinfold freckling, as well as plexiform neurofibromas detectable during early childhood. Later in life, cutaneous neurofibromas often represent important diagnostic features. NF1 is characterized by extreme clinical variability and a broad heterogeneity of NF1 gene mutations which impede genotype/phenotype correlations. Notable exceptions are NF1 microdeletions observed in 5-11 % of all NF1 patients. Patients with NF1 microdeletions frequently exhibit facial dysmorphic features and a tall stature as rather specific clinical signs. Furthermore, cutaneous and subcutaneous neurofibromas present at an early age, severe global developmental delay and cognitive disability are pathognomonic for the "NF1 microdeletion syndrome". Importantly, NF1 microdeletions are associated with an approximately twofold higher risk for malignant peripheral nerve sheath tumors than intragenic NF1 gene mutations. The severe clinical manifestations of patients with NF1 microdeletions require early multidisciplinary clinical care and frequent tumor surveillance. Therefore, when red flag features for the "NF1 microdeletion syndrome" are present in a patient, genetic testing is necessary to confirm or exclude an NF1 microdeletion.

Alterations of Ultra Long-Chain Fatty Acids in Hereditary Skin Diseases-Review Article

The skin is a flexible organ that forms a barrier between the environment and the body's interior; it is involved in the immune response, in protection and regulation, and is a dynamic environment in which skin lipids play an important role in maintaining homeostasis. The different layers of the skin differ in both the composition and amount of lipids. The epidermis displays the best characteristics in this respect. The main lipids in this layer are cholesterol, fatty acids (FAs) and ceramides. FAs can occur in free form and as components of complex molecules. The most poorly characterized FAs are very long-chain fatty acids (VLCFAs) and ultra long-chain fatty acids (ULCFAs). VLCFAs and ULCFAs are among the main components of ceramides and are part of the free fatty acid (FFA) fraction. They are most abundant in the brain, liver, kidneys, and skin. VLCFAs and ULCFAs are responsible for the rigidity and impermeability of membranes, forming the mechanically and chemically strong outer layer of cell membranes. Any changes in the composition and length of the carbon chains of FAs result in a change in their melting point and therefore a change in membrane permeability. One of the factors causing a decrease in the amount of VLCFAs and ULCFAs is an improper diet. Another much more important factor is mutations in the genes which code proteins involved in the metabolism of VLCFAs and ULCFAs—regarding their elongation, their attachment to ceramides and their transformation. These mutations have their clinical consequences in the form of inborn errors in metabolism and neurodegenerative disorders, among others. Some of them are accompanied by skin symptoms such as ichthyosis and ichthyosiform erythroderma. In the following review, the structure of the skin is briefly characterized and the most important lipid components of the skin are presented. The focus is also on providing an overview of selected proteins involved in the metabolism of VLCFAs and ULCFAs in the skin.

Genetic skin disorders: The value of a multidisciplinary clinic

Genodermatoses are inherited disorders with skin manifestations and can present with multisystem involvement, resulting in challenges in diagnosis and treatment. To address this, the expertise of dermatology and clinical genetics through a multidisciplinary clinic (Genodermatoses Clinic) were combined. A retrospective cohort study of 45 children seen between March 2018 and February 2019 in the Genodermatoses Clinic at The Children's Hospital of Philadelphia was performed. Patient demographics, referral information, genetic testing modality, diagnoses, and patient satisfaction scores were evaluated to assess the clinic's impact. The majority of patients (42.2%) were referred from Dermatology and 86.7% were referred for diagnosis. Two-thirds of the patients were recommended genetic testing, and subsequently 73.3% completed testing. Nearly three-quarters, 26 out of 36 patients (72.2%), of our undiagnosed patients received a clinical and/or molecular diagnosis, which is imperative in managing their care. Twenty-two individuals pursued genetic testing. In eight individuals (36%), molecular testing was diagnostic. However, in two individuals the molecular diagnosis did not completely explain the phenotype. However, there are still obstacles to genetic testing, such as cost of testing and insurance barriers. Almost all (91.4%) rated the Genodermatoses Clinic as "Very Good," the top Press Ganey score. High patient satisfaction scores suggest a positive impact of the Genodermatoses clinic, emphasizing the importance to increase support for the clinical and administrative time needed for patients with genodermatoses.