THE HEREDITARY SPASTIC PARAPLEGIAS (HSPs) are rapidly being understood as a
large group of genetically heterogeneous disorders in which the predominant clinical feature
is gait disturbance due to lower-extremity spasticity and weakness. The degree of severity
and manner of progression are often quite variable between different genetic types of HSP,
between different families with the same genetic type of HSP, and between affected subjects
from the same family who share exactly the same HSP gene mutation. Presently, genetic loci …