Repeat expansions in AR , ATXN1 , ATXN2 and HTT in Norwegian patients diagnosed with amyotrophic lateral sclerosis

Genetic repeat expansions cause neuronal degeneration in amyotrophic lateral sclerosis as well as other neurodegenerative disorders such as spinocerebellar ataxia, Huntington's disease and Kennedy's disease. Repeat expansions in the same gene can cause multiple clinical phenotypes. We aimed to characterize repeat expansions in a Norwegian amyotrophic lateral sclerosis cohort. Norwegian amyotrophic lateral sclerosis patients ( = 414) and neurologically healthy controls adjusted for age and gender ( = 713) were investigated for repeat expansions in , , and using short read exome sequencing and the ExpansionHunter software. Five amyotrophic lateral sclerosis patients (1.2%) and two controls (0.3%) carried ≥36 repeats in ( = 0.032), and seven amyotrophic lateral sclerosis patients (1.7%) and three controls (0.4%) carried ≥29 repeats in ( = 0.038). One male diagnosed with amyotrophic lateral sclerosis carried a pathogenic repeat expansion in , and his diagnosis was revised to Kennedy's disease. In , 50 amyotrophic lateral sclerosis patients (12.1%) and 96 controls (13.5%) carried ≥33 repeats ( = 0.753). None of the patients with repeat expansions in or had signs of Huntington's disease or spinocerebellar ataxia type 2, based on a re-evaluation of medical records. The diagnosis of amyotrophic lateral sclerosis was confirmed in all patients, with the exception of one patient who had primary lateral sclerosis. Our findings indicate that repeat expansions in and are associated with increased likelihood of developing amyotrophic lateral sclerosis. Further studies are required to investigate the potential relationship between repeat expansions and amyotrophic lateral sclerosis.