Louise Benarroch, Jovan Pešović, Marzia Rossato, Zhongbo Chen, Morghan C Lucas, Guillaume Cogan, Indhu-Shree Rajan-Babu, Vitus Prokosch, Christina Zarouchlioti, Marco Carlomagno, Ida Höijer, Mayra Sauer, Ismail Jamail, Shota Shibata, Glen Lester Sequiera, Benjamin P Kleinstiver, Sonia Lameiras, Ricardo Mouro Pinto, Giuseppe Novelli, Davina Hensman Moss, Natalia Dominik, Mathieu Barbier, Isabelle Le Ber, Guillaume Bassez, Denis Furling, Massimo Delledonne, Karen Usdin, Sylvain Baulande, Geneviève Gourdon, Birgitt Schüle, Dušanka Savić-Pavićević, Annalisa Botta, Alice E Davidson, Adam Ameur, Vincent Dion, Stéphanie Tomé, LRS-RED Consortium
Repeat-expansion disorders (REDs) are a mechanistically and clinically well-defined subgroup of rare diseases caused by the expansion of short tandem repeats (STRs). These expansions can exceed several kilobases and show complex features, such as noncanonical secondary structures, somatic instability, repeat interruptions and allele-specific methylation. These characteristics are highly relevant for understanding disease mechanisms, clinical variability, prognosis and potentially therapeutic decision-making, but cannot be fully resolved using traditional diagnostic methods or short-read sequencing technologies. By contrast, long-read sequencing (LRS) enables accurate investigation of STR complexity in a single assay, facilitates the discovery of new pathogenic repeat expansions and drives advances in diagnostics, clinical and basic research, which may allow for better patient stratification in future clinical trials. This Perspective discusses recent LRS-driven discoveries, methodological and bioinformatic advances, and emerging diagnostic applications to illustrate the potential of LRS in reshaping both research and clinical practice.