Six cases of SCA3/MJD patients that mimic hereditary spastic paraplegia in clinic

Abstract Background Spinocerebellar ataxia type 3/Machado–Joseph disease (SCA3/MJD) is an autosomal dominant neurodegenerative disease characterized by cerebellar ataxia associated with varying phenotypic variability. It was reported that a few of SCA3/MJD patients showed marked spastic paraplegia with or without cerebellar ataxia, which was partially first diagnosed as hereditary spastic paraplegia (HSP) and considered to be a new subtype (subtype V). But the data in China is still absent. Objective To investigate the mutation frequency and clinical features of subtype V of SCA3/MJD in Chinese patients with HSP. Methods Mutation detection of MJD1 gene was carried out in 46 AD-HSP families and 58 sporadic cases. Results Expanded CAG repeats that ranged from 64 to 81 of MJD1 gene were found in six probands from 46 AD-HSP families (13%, 6/46). No abnormal repeat expansion was found in sporadic cases (0/58). The initial symptoms of six SCA3 cases were all spasticity in the lower limbs, and nystagmus, dysphagia and dysarthria that occurred with disease progression seemed more frequent than HSP. Conclusion Subtype V of SCA3/MJD is not rare in China, but it is hard to distinguish between HSP and SCA3/MJD only by clinical manifestation and MRI, and MJD1 gene should be detected routinely in the patients diagnosed as HSP in clinic.