A Natural History Study of Patients With GNE Myopathy and GNE-Related Diseases

This is a prospective observational study to evaluate patients with GNE myopathy and other GNE-related diseases. The GNE gene encodes for UDP-GlcNAc 2-epimerase/ManNAc kinase, the bifunctional enzyme that initiates and regulates intracellular sialic acid (Neu5Ac) biosynthesis and glycan sialylation. GNE myopathy is a rare, autosomal recessive myopathy with onset in early adulthood characterized by progressive skeletal muscle atrophy and weakness. The impairment of Neu5Ac production is presumed to cause decreased sialylation of muscle glycoproteins, resulting in muscle deterioration. Other GNE-related diseases such as congenital thrombocytopenia have been recently identified, but the pathophysiology is not well understood. In this protocol, we plan to evaluate patients with GNE myopathy and other GNE-related diseases clinically, biochemically, and molecularly to characterize the mechanisms of disease, to delineate the natural history, phenotypes, progression and complications of GNE-related diseases, and to identify endpoints and biomarkers to support clinical trials testing potential therapies.