Linkage of a locus for autosomal dominant familial spastic paraplegia to chromosome 2p markers.

'Pure' autosomal dominant familial spastic paraplegia (SPG) is a neurodegenerative disease which clinically manifests as spasticity of the lower limbs. Dominantly inherited SPG is known to be clinically heterogenous and has been classified into late-onset and early-onset types, based on the age of onset of symptoms. We tested five autosomal dominant SPG families for genetic linkage and established linkage to chromogene 2p markers (Z(theta) = 3.65) with evidence of genetic locus heterogeneity. Three late-onset SPG families and one early-onset SPG family had high posterior probability of linkage (P > 0.94) to chromosome 2p, while the fifth family (a very early-onset family) was not linked to chromosome 2 and showed high probability of linkage to chromosome 14q. These data provide a basis for a classification of SPG according to chromosome location rather than age of onset of symptoms.