Disorders in a unique type of posttranslational modification of a-dystroglycan lay at a background of a group of congenital muscular dystrophies, called dystroglycanopathies. To bind laminin in a basal membrane the protein has to be glycosylated in a special way, with mannose linked with O-glycosidic bond to serine or threonine in a mucin-like region. The nascent glycan is then elongated with N-acetylglucosamine, galactose, sialic acid and optionally fucose. It is also suggested that proper function of dystroglycan depends on mannose phosphorylation. Six genes are involved in the molecular pathoge- nesis of dystroglycanopathies: POMT-1, POMT-2, POMGnT-1, FKT, FKRP and LARGE. The former three are proved, and the further putative glycosyltransferases of O-mannosylation pathway. The mechanisms of dystroglycanopathy once again underline the peculiar regulatory role of glycosylation, indispensable for a proper function of particular proteins.