Qualitative or quantitative defects of protein involved in O-glycosylation of alpha-dystroglycan

Qualitative or quantitative defects of protein involved in O-glycosylation of alpha-dystroglycan (Orphanet code 207113) refers to a group of rare genetic disorders collectively known as dystroglycanopathies or alpha-dystroglycanopathies. These conditions arise from mutations in genes encoding proteins responsible for the proper O-glycosylation (sugar modification) of alpha-dystroglycan, a key cell-surface protein that links the intracellular cytoskeleton to the extracellular matrix. When alpha-dystroglycan is not properly glycosylated, it cannot bind its extracellular ligands (such as laminin, agrin, and neurexin), leading to disruption of tissue integrity in skeletal muscle, the brain, and the eyes. The clinical spectrum of dystroglycanopathies is extremely broad, ranging from the most severe forms — Walker-Warburg syndrome (WWS) and muscle-eye-brain disease (MEB) — to milder presentations such as certain forms of limb-girdle muscular dystrophy (LGMD). Severe forms present at birth or in early infancy with profound muscular dystrophy (congenital muscular dystrophy), structural brain malformations including cobblestone lissencephaly, cerebellar abnormalities, hydrocephalus, and eye anomalies such as retinal detachment, microphthalmia, and cataracts. Milder forms may present later in childhood or adulthood with progressive limb-girdle muscle weakness, elevated serum creatine kinase, and variable or absent brain and eye involvement. Intellectual disability and epilepsy may also occur across the spectrum. Multiple genes have been implicated in this group, including POMT1, POMT2, POMGnT1, FKTN (fukutin), FKRP, LARGE1, ISPD (CRPPA), GMPPB, DPM1, DPM2, DPM3, B3GALNT2, B4GAT1, TMEM5 (RXYLT1), SGK196 (POMK), DAG1, and others. There is currently no cure for dystroglycanopathies. Treatment is supportive and multidisciplinary, including physical therapy, orthopedic management, respiratory support, seizure management, nutritional support, and ophthalmologic and neurodevelopmental care. Research into gene therapy and pharmacological approaches to restore glycosylation is ongoing but remains experimental.

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