Prospective natural history study of ALS clinical characteristics and biomarkers.

Objective: To define the natural history of the amyotrophic lateral sclerosis (C9ALS) patient population, develop disease biomarkers, and characterize patient pathologies.

Methods: We prospectively collected clinical and demographic data from 116 symptomatic C9ALS and 12 non-amyotrophic lateral sclerosis (ALS) full expansion carriers across 7 institutions in the United States and the Netherlands. In addition, we collected blood samples for DNA repeat size assessment, CSF samples for biomarker identification, and autopsy samples for dipeptide repeat protein (DPR) size determination.