FKTN (fukutin) is a glycosyltransferase that catalyzes the transfer of ribitol-phosphate from CDP-ribitol to the distal N-acetylgalactosamine of phosphorylated O-mannosyl trisaccharide on alpha-dystroglycan, initiating formation of the ribitol 5-phosphate tandem repeat required for ligand binding 123. FKTN is essential for proper localization and activity of POMGNT1 in Golgi membranes and participates in a complex linking muscle membrane structures 45. Mechanistically, FKTN functions in protein O-linked glycosylation via mannose, operating within the cis-Golgi network and endoplasmic reticulum [GO annotations]. FKTN mutations cause dystroglycanopathies, a genetically heterogeneous group of congenital muscular dystrophies affecting glycosylation of alpha-dystroglycan 6. Pathogenic FKTN variants result in various phenotypes including limb-girdle muscular dystrophy, Walker-Warburg syndrome, congenital hydrocephalus, and dilated cardiomyopathy 789. Recent evidence indicates FKTN is enriched for regulatory variants in early-onset cardiomyopathy, with functional validation in patient myocardium 10. Additionally, FKTN downregulation contributes to pleiotropic manifestations in MORC2-related disorders 11, suggesting FKTN dysfunction has broader clinical implications beyond classical dystroglycanopathies.