Overview of Hereditary Spastic Paraplegia
Hereditary spastic paraplegia (HSP) is a group of genetic, degenerative disorders of the spinal cord characterized by progressive weakness (paraplegia) and stiffness (i.e., spasticity) of the legs. Spasticity refers to excessive muscle tone (hypertonicity) or muscle overactivity with increased velocity-dependent resistance to stretch. This group of disorders is also sometimes referred to as...
HSP is often classified based upon whether progressive spasticity occurs as an isolated finding (i.e., uncomplicated or "pure" HSP) or with other neurologic abnormalities (i.e., complicated HSP). In families (kindreds) affected by complicated HSP, associated neurologic features have included mental retardation; deafness; degenerative changes of the retinas or the nerve-rich, innermost membranes of the eyes (retinopathy); impaired coordination of voluntary movements (ataxia); or progressive deterioration of thought processing and acquired intellectual abilities (dementia).
HSP may be inherited as an autosomal dominant, autosomal recessive, or x-linked recessive trait. These disorders may also be classified based upon mode of inheritance, with various subtypes as determined by the location (locus) of the disease gene. Researchers have demonstrated that HSP may be caused by changes (mutations) of several different genes (genetic heterogeneity), many of which have been mapped to certain chromosomes. Loci for autosomal dominant, autosomal recessive, and x-linked recessive HSP have been identified in various affected families (kindreds).