FKTN and neuromuscular disease caused by qualitative or quantitative defects of alpha-dystroglycan: Besides FKTN variants, dystroglycanopathy type A is caused by homozygous or compound heterozygous mutations in all other genes responsible for dystroglycanopathies, and no clear genotype–phenotype correlation has yet been achieved, even if clinical severity seems to inversely correlate with the residual enzymatic activity (Mercuri et al., 2009).