Exome sequencing of patients with clinical characteristics of PCH1D identified a number of variants of the RNA exosome core subunit EXOSC9 (Fig. 5a and b) (Burns et al. 2018; Bizzari et al. 2020; Sakamoto et al. 2021). This evidence concerns the gene EXOSC9 and pontocerebellar hypoplasia, type 1D.