The most common expansions (in the full-mutation range; Fig. 1b) were those in C9orf72 (C9orf72-ALS/FTD) and DMPK (DM1) with a frequency of 1 in 839 and 1 in 1,786, respectively, followed by expansions in AR (SBMA: 1 in 2,561 males) and HTT (HD: 1 in 4,109). The gene discussed is HTT; the disease is frontotemporal dementia.