The prevalence of several reciprocal duplication/deletion syndromes such as CMT1A/HNPP, PTLS/SMS, dup22(q11.2q11.2)/DG/VCFS has been used to estimate the relative frequency of duplications and deletions mediated by the same pairs of LCRs. The gene discussed is PMP22; the disease is Potocki-Lupski syndrome.