In our cohort, ≥27 CAG repeats in ATXN2 were associated with a higher risk of developing ALS (odds ratio [OR] = 2.666 [1.471–4.882]; p = 0.0013) but not FTD (odds ratio [OR] = 1.446 [0.558–3.574]; p = 0.44). This evidence concerns the gene ATXN2 and frontotemporal dementia.