Spastic paraplegia type 4 (SPG4) is the most common type of autosomally inherited spastic paraplegia. Its main clinical features include typical simple hereditary spastic paraplegia, with neurological impairments limited to lower limb spasticity, hypertonic bladder dysfunction, and mild weakening of lower limb vibration sensation, without accompanying features such as nerve atrophy, ataxia, cognitive impairment, seizures, and muscle tone disorders. SPAST is the main pathogenic gene underlying SPG4, and various pathogenic SPAST variants have been discovered. This disease has featured a high degree of clinical heterogeneity, and the same pathogenic variant can have different age of onset and severity among patients and even within the same family. There is a lack of systematic research on the correlation between the genotype and phenotype of SPG4, and the pathogenic mechanism has remained controversial. This article has provided a review for the clinical characteristics, pathogenic gene characteristics, correlation between the genotype and phenotype, and pathogenic mechanism of this disease, with an aim to provide reference for its clinical diagnosis and treatment.

Neurodegenerative disease; Hereditary spastic paraplegia type 4; SPAST gene; Clinical heterogeneity