Spastic paraperesis is an inherited disorder in which the person's leg muscles grow more spastic over time, according to the Journal of Neurology, Neurosurgery & Psychiatry. It is also called Strümpell-Lorrain syndrome.
Spastic paraperesis is actually the name for a group of these disorders, claims WebMD. As of 2015, over 50 subtypes of this disorder have been identified.
People with the "pure" form of the disease usually only experience spasticity of the lower limbs, according to the National Organization for Rare Disorders. They have a normal lifespan and normal strength in their arms and hands. People who have other subtypes of the disease experience urinary urge or incontinence, seizures and strange sensations in the lower extremities. Patients also experience dementia and disturbances in their vision and hearing, and some also suffer mental retardation and problems speaking and swallowing. The reflexes in the lower limbs can be exaggerated, and they have feet with unusually high arches.
The symptoms and the progression of the disease are different for different patients. The subtypes of spastic paraperesis are due to mutations in genes, claims the National Organization for Rare Disorders. The genes can be passed from one parent or both parents. Some forms of the disorder are linked to the X chromosome and affect male children. Female children don't have symptoms, but are carriers of the disease.