Compared with other diseases in which nonrecurrent duplications have been analyzed in detail such as PMD, developmental delay caused by MECP2 duplications and Potocki-Lupski microduplication syndrome (PTLS), the percentage of complex duplications in ADLD appears to be much lower [Carvalho et al., 2009; Lee et al., 2007; Zhang et al., 2009a; 2009b]. The gene discussed is MECP2; the disease is adult-onset autosomal dominant demyelinating leukodystrophy.