Hereditary spastic paraplegia (HSP) is a group of clinically and genetically diverse disorders that share a primary feature, which is the causation of progressive and generally severe lower extremity weakness and spasticity. The prevalence is estimated to range between 1.3 to 9.6 cases per 100,000 people. HSP classifications are based on the mode of inheritance and genetic linkage. This disorder may segregate as an autosomal dominant, autosomal recessive, X-linked or mitochondrial trait. To date, 72 different spastic disease-loci have been identified, and 55 spastic paraplegia genes (SPGs) have already been cloned.
Autosomal recessive spastic paraplegia type 18 (SPG18) is a rare, complex type of HSP that presents in early childhood. It is characterized by progressive spastic paraplegia associated with delayed motor development, severe intellectual disability and joint contractures. There is no treatment that can prevent or reverse nerve degeneration in HSP.