A case report of late-onset cerebellar ataxia associated with a rare p.R342W TGM6 (SCA35) mutation.

Background: Mutations in TGM6 gene, encoding for transglutaminase 6 (TG6), have been implicated in the pathogenesis of spinocerebellar ataxia type 35 (SCA35), a rare autosomal dominant disease marked by cerebellar degeneration and characterized by postural instability, incoordination of gait, features of cerebellar dysfunction and pyramidal signs.
Case Presentation: Here we report the case of an Italian patient with late-onset, slowly progressive cerebellar features, including gait ataxia, scanning speech and ocular dysmetria and pyramidal tract signs. Whole exome sequencing revealed the rare heterozygous c.1024C > T (p.R342W) variant of TGM6, located at a highly evolutionary conserved position and predicted as pathogenic by in silico tools. Expression of TG6-R342W mutant in HEK293T cells led to a significant reduction of transamidase activity compared to wild-type TG6.
Conclusion: This finding extends SCA35 genetic landscape, highlighting the importance of TGM6 screening in undiagnosed late-onset and slowly progressive cerebellar ataxias.