Two other EXOSC9 variants that replace glycine 51 with arginine (EXOSC9-G51R) or leucine 80 with arginine (EXOSC9-L80R) have been identified in patients with PCH1D, but these variants have not been subjected to any functional analysis. This evidence concerns the gene EXOSC9 and pontocerebellar hypoplasia, type 1D.