Expansion of the mutation and phenotypic spectrum of hereditary spastic paraplegia

Background: Hereditary spastic paraplegias (HSPs) are a heterogeneous group of rare neurodegenerative disorders affecting the corticospinal tracts, and more than 80 HSP loci have been mapped to cause HSP. In this study, we aim to perform a genetic and clinical study of ten (6 male, 4 female) sporadic Chinese HSP patients.

Methods: Next-generation sequencing (NGS) gene panels combined with multiplex ligation-dependent probe amplification assay (MLPA) analysis and the trinucleotide repeat dynamic mutation detection are available for the ten patients.

Results: Among the 10 patients, one SPG7 patient, one SPG11 patient, and one pure SPG31 patient were detected. Two variants (deletion of exon 3-9 of SPG7 gene and the heterozygous mutation c.1861C > T/p.Q621* of SPG11 gene) were novel and three (c.1150_1150 + 1insCTAC/p.G384Afs*13 in SPG7 gene, c.3075dupA/p.E1026Rfs*4 in SPG11 gene, and c.478delA/p.R160Gfs*63 of REEP1 gene/SPG31) were previously reported. The SPG11 patient presented mild intellectual with peripheral neuropathy and thin corpus callosum (TCC) with no white matter abnormalities (WMA). The SPG7 patient detected in this study is the third SPG7 family reported in China; he manifested peripheral neuropathy, scoliosis, and polydactyly which expand the phenotype spectrum of SPG7.

Conclusions: The AAO overlapped among each HSP subtype, which limited the ability to predict the subtype of HSP from AAO. Compared with non-Asian patients, the mutation frequency of SPG7 is relatively low in Asian populations. Considering the varieties of mutation types of HSP, we suggested targeted sequencing gene panels should be combined with MLPA for diagnosis of HSP.