Footnotes

• Twitter @irongraft

• Contributors FS: study concept and design, drafting and revising of manuscript, acquisition and interpretation of data. SM: data acquisition, revising the manuscript critically for content, study supervision. SAH: genetic test for HD in Oman, data and DNA collection, revising and approval of manuscript. QAS: data acquisition accuracy, logistic support at Royal Hospital, critical review and approval of the manuscript. BD: data acquisition accuracy and integrity, critical review and approval of the manuscript. GC: reviewed the epidemiological study design and provided critical review and approval of the manuscript. TM: designed statistical analysis, was involved in the data analysis and provided critical review of the manuscript. All authors gave final approval of the version to be published.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests FS provided consulting services and advisory board functions to Teva, Pfizer, Hoffmann-La Roche, Novartis, PTC Therapeutics, UCB, Oman Ministry of Health - Sultanate of Oman. He is cofounder, scientific officer and consultant of the not-for-profit organisation Italian League for Research on Huntington disease (LIRH Foundation).

• Patient consent for publication Not required.

• Ethics approval Institutional Review Board of LIRH Foundation (Prot. 1.050219/mob) and Ethical Committee, Directorate General of the Royal Hsopital, Ministry of Health, Muscat, Sultanate of Oman (reference number: SRC#31/2020).

• Provenance and peer review Not commissioned; externally peer reviewed.