Editor—Hereditary spastic paraplegia, spastic paraplegia, or familial spastic paraplegia (HSP, SPG, or FSP) are a heterogeneous group of syndromes characterised by degeneration of corticospinal tracts. Currently, two loci for the X linked recessive type are well established, at Xq28 (SPG1, MIM 312900)1 and at Xq22 (SPG2, MIM 312920).2 3 Six loci for the autosomal dominant type have been reported, at 14q12-q23 (SPG3, MIM 182600),4 at 2p21-p24 (SPG4, MIM 182601),5 6 at 15q11.1 (SPG6, MIM 600363),7 at 8q23-q24 (SPG8, MIM 603563),8at 10q23.3-q24.1 (SPG9, MIM 601162),9 and at 12q13 (SPG10, MIM 604187).10 Two loci for the autosomal recessive type were mapped to 8p12-q13 (SPG5A, MIM 270800)11 and to 16q24.3 (SPG7, MIM 602783),12 13 respectively.

HSPs are clinically subdivided into pure and complicated forms. The autosomal dominant form can be complicated by dementia and epilepsy.14 The X linked form can be more severe if combined with ataxia, absent extensor pollicis longus, and involvement of cerebral cortex and optic nerves (SPG1). The complicated autosomal recessive type is rare and is described as microcephaly with spastic quadriplegia (MIM 251280).15-19 The fact that familial cases were reported, where no linkage to any of the previously mentioned loci could be found, suggests that additional gene loci for hereditary spastic paraplegia exist.20 21 The genetic heterogeneity supports the concept of a multitude of different genes responsible for spastic paraplegia. Since, however, a marked clinical similarity is found within HSP families with positive linkage to each of the reported loci, it was proposed that gene products from HSP loci may participate in a common biochemical cascade which, if disturbed, results in axonal degeneration that is most pronounced at the ends of the longest …