Phenotypical differences of gene-positive and negative amyotrophic lateral sclerosis: a comparative case series.

Background: Hexanucleotide repeat expansions of account for a significant proportion of autosomal dominant neurodegenerative diseases in the amyotrophic lateral sclerosis (ALS)-frontotemporal dementia spectrum. In the absence of a family history, clinical identification of such patients remains difficult. We aimed to identify differences in demographics and clinical presentation between patients with gene-positive ALS (C9pALS) versus gene-negative ALS (C9nALS), to aid identification of these patients in the clinic and examine differences in outcomes including survival.