Problems of Unknown Significance: Counseling in the Era of Next Generation Sequencing

Die Bedeutung der Hochdurchsatz-Sequenzierung in der medizinisch genetischen Diagnostik und Beratung

Next-Generation-Sequencing ist ein modernes diagnostisches Hochdurchsatz-Verfahren (Multi-Gen-Analysen), durch dessen Einsatz sowohl hereditäre Krebserkrankungen (Tumordispositionssyndrome, Keimbahndiagnostik) als auch somatische Alterationen in Tumoren besser abgeklärt werden können. Der breitere Einsatz dieser Technologie im medizinischen Alltag zeigt das tatsächliche Ausmaß der interindividuellen genetischen Variabilität. Wichtige Bedeutung hat dieses Verfahren für die Untersuchung von heterogenen genetischen Erkrankungen (z. B. Tumorerkrankungen, neurodegenerativen und -muskulären Erkrankungen) erlangt. Weitere Indikationsgebiete stellen die Pharmakogenetik sowie die nicht invasive Pränataldiagnostik dar. Es ist zu erwarten, dass dieses diagnostische Mittel eine breite klinische Anwendung finden wird. Mit der rasanten Zunahme und Komplexität genetischer Dateninformationen nimmt die richtige Interpretation und Übermittlung der Befunde in der humangenetischen Beratung (Keimbahndiagnostik) einen hohen Stellenwert ein. Die genetische Beratung muss entsprechend neu ausgerichtet und adaptiert werden.

Variants of uncertain significance in the era of next-generation sequencing

ABSTRACT

Next-generation sequencing (NGS) is now widely used in diagnosing rare diseases. However, it has some limitations, such as variants of uncertain significance (VUS). This can present difficulties even for nurse practitioners involved in clinical genetics. We present three cases from our clinical practice: two targeted panel testing and one exome sequencing. Whole blood samples were collected and sent for NGS analysis. In case 1, a VUS was found in the LITAF gene, which is associated with autosomal dominant Charcot-Marie-Tooth disease type 1C. In case 2, a VUS was reported in the MEFV gene, which is associated with autosomal recessive and autosomal dominant familial Mediterranean fever. In these cases, the reported VUS corresponded to the clinical diagnosis. In case 3, two variants in the heterozygous state were found in the ATP7B gene, which is associated with Wilson disease, and the disorder was later clinically recognized. According to the published guidelines, VUSs should not be discussed as a cause for an observed genetic condition. Nevertheless, if the reported variant is in a gene associated with the clinically diagnosed disorder, and there is a strong genotype-phenotype correlation, it could be suggestive of the etiological role of this variant.

Current scenario of the genetic testing for rare neurological disorders exploiting next generation sequencing

Next generation sequencing is currently a cornerstone of genetic testing in routine diagnostics, allowing for the detection of sequence variants with so far unprecedented large scale, mainly in genetically heterogenous diseases, such as neurological disorders. It is a fast-moving field, where new wet enrichment protocols and bioinformatics tools are constantly being developed to overcome initial limitations. Despite the as yet undiscussed advantages, however, there are still some challenges in data analysis and the interpretation of variants. In this review, we address the current state of next generation sequencing diagnostic testing for inherited human disorders, particularly giving an overview of the available high-throughput sequencing approaches; including targeted, whole-exome and whole-genome sequencing; and discussing the main critical aspects of the bioinformatic process, from raw data analysis to molecular diagnosis.

Telomeropathies: Etiology, diagnosis, treatment and follow-up. Ethical and legal considerations

Telomeropathies involve a wide variety of infrequent genetic diseases caused by mutations in the telomerase maintenance mechanism or the DNA damage response (DDR) system. They are considered a family of rare diseases that often share causes, molecular mechanisms and symptoms. Generally, these diseases are not diagnosed until the symptoms are advanced, diminishing the survival time of patients. Although several related syndromes may still be unrecognized this work describes those that are known, highlighting that because they are rare diseases, physicians should be trained in their early diagnosis. The etiology and diagnosis are discussed for each telomeropathy and the treatments when available, along with a new classification of this group of diseases. Ethical and legal issues related to this group of diseases are also considered.