“…1 Several types of HSP have been mapped to different loci, demonstrating extensive genetic heterogeneity. AD-HSP has been mapped to chromosome 14q11.2-q24.3 (SPG3) in French, American, German and Tibetan families, [2][3][4][5] to chromosome 2p21-p24 (SPG4) in French, Dutch, North American, Tunisian, Belgian and German families, 3,[6][7][8] to 15q (SPG6) in one family of Irish descent, 9 to 8q23-24 (SPG8) in a North American kindred of German descent and in an English family 10,11 and to 12q13 (SPG10) in an English family. 12 There must be at least one further AD-HSP locus, since in one family linkage to all these five loci has been excluded.…”