GNE and GNE myopathy: GNE myopathy is caused by mutations in the GNE gene encoding a bifunctional enzyme [uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase and N-acetylmannosamine kinase] that catalyzes two rate-limiting reactions in cytosolic sialic acid synthesis [3-7].