Analysis of CACNA1A CAG repeat lengths in patients with familial ALS

Intermediate-length ATXN2 CAG repeats are a risk factor for amyotrophic lateral sclerosis (ALS). Here we report on a female patient with heterozygous repeat expansion mutation in the CACNA1A gene presenting with a pure ALS syndrome while her father, who also carries that CACNA1A mutation, suffers from a classical spinocerebellar ataxia type 6. Hypothesizing that CACNA1A CAG repeat expansions could be a monogenic cause for familial ALS (fALS), we analyzed the CAG repeat lengths in CACNA1A in a large cohort of genetically unexplained patients with fALS. Our results indicate that CAG repeat expansion mutations in CACNA1A are not a frequent monogenic cause of fALS but could phenotypically present as ALS in rare instances.