C9orf72 hexanucleotide repeat in Huntington-like patients: Systematic review and meta-analysis

The protocol was registered on the International Prospective Register of Systematic Reviews database (PROSPERO) (registration number: CRD42018105465). The search was carried out in Medline, Scopus, Web of Science, and Embase in April 2018. Observational studies reporting patients with HLD carrying the hexanucleotide repeat expansion in the C9orf72 gene were selected and revised; this process was carried out in duplicate. The cutoff threshold for considering the hexanucleotide expansion as a pathogenic variant was equal or more than 30 G4C2 repeats. The pooled frequency and 95% CI were calculated with random effect models.