Hereditary spastic paraplegia

Hereditary spastic paraplegia (HSP) is a group of inherited neurological disorders characterized by progressive weakness (paraplegia) and increased muscle tone and stiffness (spasticity) of leg muscles. HSP is also sometimes referred to as familial spastic paraplegia (FSP) or Strumpell-Lorraine syndrome. The age at symptom onset and the degree of muscle weakness and spasticity may be extremely variable from case to case, including among individuals within the same family (kindred). According to reports in the medical literature, symptom onset may occur as early as infancy or as late as the eighth or ninth decade of life; however, symptoms may most often develop during early to mid-adulthood. Initial findings typically include stiffness and relatively mild weakness of leg muscles, balance difficulties, unexplained tripping and falls, and an unusually "clumsy" manner of walking (gait). As the disorder progresses, walking may become increasingly difficult. However, complete loss of the ability to walk is relatively rare.

HSP may be classified into two major subtypes: "uncomplicated" or "complicated" HSP. In individuals with uncomplicated (or "pure") HSP, progressive spastic paraplegia occurs as an isolated, primary finding. In those with complicated HSP, additional neurologic abnormalities are present. Some individuals with uncomplicated HSP may develop muscle spasms and difficulties with bladder control. In those with complicated HSP, associated symptoms and findings may include visual and/or hearing impairment, mental retardation, impaired control of voluntary movements (ataxia), and/or other abnormalities.

According to researchers, changes (mutations) of many different genes may cause HSP. In most cases, such mutations appear to be transmitted as an autosomal dominant trait. More rarely, mutations for HSP may be inherited as an autosomal recessive or X-linked recessive trait. The basic underlying defect or defects in HSP are unknown. However, associated symptoms appear to result from progressive degenerative changes of regions of the spinal cord (corticospinal tracts) that convey motor impulses from the brain to muscles involved in controlling certain voluntary movements.