- Nonaka myopathy is caused by mutations in the UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase gene (GNE). Kayashima, T., Matsuo, H., Satoh, A., Ohta, T., Yoshiura, K., Matsumoto, N., Nakane, Y., Niikawa, N., Kishino, T. J. Hum. Genet. (2002)