Positional cloning led to the identification of the first molecular defects in X-linked EDMD on chromosome Xq28 in the STA gene (now called EMD) (Bione et al., 1994), followed a few years later by the identification of a mutation on chromosome 1q21 in the LMNA gene (Bonne et al., 1999). The gene discussed is EMD; the disease is Emery-Dreifuss muscular dystrophy.