PRX and hereditary disease: Some genetic diseases also lead to a reduced internodal length outcome: Periaxin and Laminin 2 (also called Merosin) mutations induce short myelin sheath internodes in peripheral nerves and lead to CMT4F and Lama2 neuromuscular disease respectively (Gillespie et al., 2000; Guilbot et al., 2001; Di Muzio et al., 2003).