G6PC1 and autosomal recessive severe congenital neutropenia due to G6PC3 deficiency: Several mutations of residues that are identical between G6PC1 and G6PC3 have been associated with GSD type 1a and Dursun syndrome, respectively [55,56], supporting the notion that SNPs that alter conserved residues in all three G6PC1 isoforms will likely have similar effects on enzyme activity because catalytically important residues are conserved in all three isoforms.