Hereditary spastic paraplegia (HSP) is a group of inherited diseases whose main feature is a progressive gait disorder. The disease presents with progressive stiffness (spasticity) and contraction in the lower limbs. HSP is also known as hereditary spastic paraparesis, familial spastic paraplegia, French settlement disease, Strumpell disease, or Strumpell-Lorrain disease. The symptoms are a result of dysfunction of long axons in the spinal cord. The affected cells are the primary motor neurons; therefore, the disease is an upper motor neuron disease. HSP is not a form of cerebral palsy even though it physically may appear and behave much the same as spastic diplegia. The origin of HSP is different from cerebral palsy. Despite this, some of the same anti-spasticity medications used in spastic cerebral palsy are sometimes used to treat HSP symptoms. HSP is caused by defects in transport of proteins, structural proteins, cell-maintaining proteins, lipids, and other substances through the cell. Long nerve fibers (axons) are affected because long distances make nerve cells particularly sensitive to defects in these mentioned mechanisms. The disease was first described in 1880 by the German neurologist Adolph Str¨¹mpell. It was described more extensively in 1888 by Maurice Lorrain, a French physician. Due to their contribution in describing the disease, it is still called Str¨¹mpell-Lorrain disease in French-speaking countries. The term hereditary spastic paraplegia was coined by Anita Harding in 1983.

Reference
Wiki: Spastic paraplegia