Ryan M, et al. - Researchers conducted this prospective population-based parent-offspring heritability study to discover the extent of amyotrophic lateral sclerosis (ALS) heritability and evaluate how sex is connected to disease transmission. During the study period, a total of 32 parent-child ALS dyads were recognized. Investigators found that there is a genetic basis for up to 50% of the variance in ALS and that the presence of the variant C9orf72 is an important determining factor for heritability. Compared to the general population, first degree relatives of people with ALS with no known genetic basis continue to be at increased risk of developing ALS. A previously unrecognized sex-mediated impact was inferred by a greater estimate of heritability in mother-daughter pairings.