The Silver Syndrome Variant of Hereditary Spastic Paraplegia Maps to Chromosome 11q12-q14, with Evidence for Genetic Heterogeneity within This Subtype

The hereditary spastic paraplegias (HSPs) are a complex group of neurodegenerative disorders characterized by lower-limb spasticity and weakness. Silver syndrome (SS) is a particularly disabling dominantly inherited form of HSP, complicated by amyotrophy of the hand muscles. Having excluded the multiple known HSP loci, we undertook a genomewide screen for linkage of SS in one large multigenerational family, which revealed evidence for linkage of the SS locus, which we have designated “ SPG17,” to chromosome 11q12-q14. Haplotype construction and analysis of recombination events permitted the minimal interval defining SPG17 to be refined to ∼13 cM, flanked by markers D11S1765 and D11S4136. SS in a second family was not linked to SPG17, demonstrating further genetic heterogeneity in HSP, even within this clinically distinct subtype.