For example, when P18 and P19 with mutations in B3GALNT2 and P20 and P21 with mutations in GMPPB were first analysed by flow cytometry, variants in these genes had not yet been identified as the cause of a dystroglycanopathy. Here, B3GALNT2 is linked to neuromuscular disease caused by qualitative or quantitative defects of alpha-dystroglycan.