Indeed, 5S expression has been shown to be unaffected in HEK293 cells harboring a pathogenic POLR3A variant associated with a typical POLR3-related leukodystrophy phenotype, increased in blood from patients with an atypical striatal form of POLR3-related leukodystrophy, and yet decreased in fibroblasts from patients with POLR3K mutations (Azmanov et al., 2016; Dorboz et al., 2018; Choquet et al., 2019). This evidence concerns the gene POLR3K and leukodystrophy.