C9ORF72 Intermediate Repeat Expansion in a Patient With Psychiatric Disorders and Progressive Cerebellar Ataxia

Large expansions of the noncoding GGGGCC repeat (more than 30) in the first intron of the C9ORF72 gene have been demonstrated to cause amyotrophic lateral sclerosis and frontotemporal dementia. Recent papers have investigated the possible pathogenic role and associated clinical phenotypes of hexanucleotide expansions with intermediate repeat lengths ranging between 20 and 29 repeats.

We report a case of a 71-year-old Sardinian female patient with a long history of psychiatric disorders such as mixed anxiety-depressive disorder associated with somatization disorder and histrionic personality who developed a slowly progressive cerebellar syndrome, mild cognitive impairment, pyramidal signs, and rapid eye movement sleep behavior disorder with imaging abnormalities on the DaTSCAN single-photon emission computed tomography indicating an alteration in the presynaptic dopaminergic system. The patient was found to have intermediate C9ORF72 repeat expansions.

Early psychiatric presentations are a recurrent phenotypic manifestation of C9ORF72 expansions. In our patient, the intermediate C9ORF72 repeat expansion may have a pathogenic role in the cooccurrence of psychiatric and sleep disorders, cognitive dysfunctions, pyramidal system involvement, and late-onset cerebellar ataxia. This observation widens the spectrum of neurodegenerative conditions linked to C9ORF72 mutations.