Previous studies have shown that the somatic heterogeneity of the repeat sizes is quite common in similar repeat expansion disorders, such as ALS/FTD caused by the C9orf72 and SCA10 caused by the ATXN10. (Matsuura et al., 2004; Ebbert et al., 2018) However, the somatic heterogeneity of SCA36 has only been mentioned in the literature and has not been described in detail. Here, C9orf72 is linked to frontotemporal dementia.