Skip to Content


MDS makes every effort to publish accurate information on the website. "Google Translate" is provided as a free tool for visitors to read content in one's native language. Translations are not guaranteed to be 100% accurate. Neither MDS nor its employees assume liability for erroneous translations of website content.

International Parkinson and Movement Disorder Society
Main Content

First Tunisian study examining age of onset for biallelic mutations in Huntington’s disease

August 27, 2023

COPENHAGEN, DENMARK — The first study of its kind was released today at the International Congress of Parkinson’s Disease and Movement Disorders® in Copenhagen, Denmark. This Tunisian cohort study reported that the age of disease onset for patients with a homozygous mutation in the Huntingtin gene (HTT) did not differ significantly from that of heterozygous patients.  

Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder that is caused by CAG expansion in HTT. Homozygosity in HD is rare; therefore, its clinical and molecular features are poorly understood compared to that of heterozygous patients.  

The genetic and familial history of 180 Tunisian HD patients, five homozygous, were examined. The age of disease onset between the homozygous and heterozygous patients did not differ significantly. Patients with a large allele expansion were associated with an earlier age of onset, 30 years for homozygous and 33 years for heterozygous. Patients with smaller all were associated with a later age of onset, 62 years for homozygous and 74 years for heterozygous. The number of CAG repeats and age of disease onset was shown to be inversely correlated for homozygous patients.  

“Huntington's disease is a rare disease that exists all over the world," said Prof. Joaquim Ferreira MD, PhD, University of Lisbon. “However, access to genetic diagnostic tests is not available in many parts of the world, including many African countries. This study carried out in a population of Tunisian patients reminds us not only of the need to make genetic diagnostic tests available everywhere, but also of the benefit of these countries being able to contribute with scientifically relevant data. In this study, it is presented the clinical and molecular features of HD patients with homozygous alleles which is an additional contribution to understanding the relationship between the quantity of the mutated huntingtin and the disease phenomenology.” 

Full text of this abstract will be available at (Reference #909) after the embargo lifts August 27, 2023, 08:00 CEST. 

* * *  

About the 2023 MDS International Congress of Parkinson’s Disease and Movement Disorders®:  
The MDS International Congress is the premiere annual event to advance the clinical and scientific discipline of Movement Disorders, including Parkinson’s disease. Convening thousands of leading clinicians, scientists and other health professionals from around the globe, the International Congress will introduce more than 1,800 scientific abstracts and provide a forum for education and collaboration on latest research findings and state-of-the-art treatment options. 

About the International Parkinson and Movement Disorder Society: 
The International Parkinson and Movement Disorder Society® (MDS), an international society of more than 11,000 clinicians, scientists, and other healthcare professionals, is dedicated to improving patient care through education and research. For more information about MDS, visit

We use cookies to give you the best possible experience with our website. These cookies are also used to ensure we show you content that is relevant to you. If you continue without changing your settings, you are agreeing to our use of cookies to improve your user experience. You can click the cookie settings link on our website to change your cookie settings at any time. Note: The MDS site uses related multiple domains, including and This cookie policy only covers the primary and domain. Please refer to the MDS Privacy Policy for information on how to configure cookies for all other domains on the MDS site.
Cookie PolicyPrivacy Notice