Hereditary spastic paraplegia has an estimated prevalence of 1.8/100 000. Genetic cause is identified in 33%-55% of families with autosomal dominant inheritance (AD-SP) and in 18%-29% of families with autosomal recessive inheritance (AR-SP). The most frequent form of AD-SP is SPG4 (SPAST), accounting for 40% of AD-SP forms and 20% of sporadic forms (Ruano et al., 2014). SPG3A (ATL1) is the cause of 10%-15% of AD-SP cases (up to 40% in SPG4-negative cohorts), with the most frequent form starting in the first decade of life (Giudice et al., 2014). SPG11 is the most common cause of AR-SP (20%-50%) (Stevanin et al., 2008).
Anita Harding’s historical description distinguishes pure and complicated forms (Harding, 1983). The pure form presents isolated pyramidal signs such as spasticity, hyperreflexia, Babinski sign, and motor deficits, which can be associated with sphincter disorder and deep sensitivity alterations. Complicated forms comprise several clinical entities combining spastic paraplegia with other neurological/non-neurological signs such as cerebellar ataxia, optic atrophy, retinitis pigmentosa, thinning of the corpus callosum, neuropathy, or epilepsy, among others.