Dystroglycanopathy is a collective term for a group of genetic disorders caused by abnormalities in the O-mannosyl glycans of dystroglycans. One such form of dystroglycanopathy is Fukuyama congenital muscular dystrophy, which accounts for most cases in Japan [1]. Dystroglycanopathy is characterized by congenital muscular dystrophy, ocular abnormalities, and type II lissencephaly. O-mannosyl glycans on dystroglycans are essential for binding to extracellular matrix proteins such as laminin. Defective synthesis of these glycans impairs this interaction, leading to destabilization of the muscle membrane and abnormalities in neuronal migration (Fig. 80.1) [2, 3]. In recent years, research on O-mannosyl glycans has progressed from the molecular to the organismal level, facilitating the investigation of glycan-based therapeutic strategies.