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

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.

To investigate the mutation frequency and clinical features of subtype V of SCA3/MJD in Chinese patients with HSP.

Mutation detection of MJD1 gene was carried out in 46 AD-HSP families and 58 sporadic cases.

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.

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.