B3GALNT2 mutations associated with nonsyndromic autosomal recessive intellectual disability reveal a lack of genotype– phenotype associations in the muscular dystrophy-dystroglycanopathies

The phenotypic severity of congenital muscular dystrophy-dystroglycanopathy (MDDG) syndromes associated with aberrant glycosylation of α-dystroglycan ranges from the severe Walker-Warburg syndrome or muscle-eye-brain disease to mild, late-onset, isolated limb-girdle muscular dystrophy without neural involvement.