SPG11 and hereditary spastic paraplegia: Two of them carried mutations in SPG11. Combined with our previous study [15], the number of AR-HSP families in our cohort was 17, and the frequency of SPG11 mutations in AR-HSP were 23.5% (4/17), which was a bit less than that in the Caucasian population (30.9%, 30/97) [9] and a recent study in the Chinese population (33.33%, 12/36) [12].