Definition of Spastic paraplegia, autosomal dominant Spastic
paraplegia, autosomal dominant: A degenerative disorder of
nerves with progressive spasticity of the legs. Abbreviated as
AD-HSP. Spasticity is a state of increased muscle tone.
Paraplegia refers to the legs (quadriplegia refers to both the
arms and legs). In hereditary spastic paraplegia there is an
insidiously progressive condition characterized by weakness
beginning in the feet and lower legs. There is stiffness of the
legs in walking due to the spasticity. Autosomal dominant
hereditary spastic paraplegia can result from changes in a
number of different genes. Each gene is autosomal (on an nonsex
chromosome) and dominant (capable of causing the disease by
itself). Among the 4 genes causing AD-HSP found through 1999,
one that is on chromosome 2 accounts for 40-50% of all families
with AD-HSP. Researchers have identified a gene that is
responsible for this most frequent form of AD-HSP. They named
the gene "spastin" (for spasticity). Spastin appears