On the other hand, other missense variants at the same codon (Y329S and Y329F) have been identified in patients with either GSDIV or adult polyglucosan body disease [35, 38], highlighting the functional importance of the Y329 residue in the GBE1 protein and supporting the association of this variant with the disease. This evidence concerns the gene GBE1 and glycogen storage disease due to glycogen branching enzyme deficiency.