We aim to analyze YOHD patients to better understand disease characteristics and progression.

Huntington’s disease (HD) is a genetic, progressive neuropsychiatric disease with typical age of onset in range of 30-50 years, though it may present from childhood to late adulthood. Previous studies have clearly defined subsets of HD patients which include adult onset, late onset and juvenile HD (JHD) with distinct features. Expert observations made in our HD population have identified a cohort of patients with onset of disease between the ages of 20 to 30 who demonstrate a distinct clinical course. We have name this cohort  young-onset (YO) Huntington’s Disease.

This is an EMR review of YOHD patients at the UC Davis HD Center of Excellence from 2004 to 2021. Inclusion Criteria: Clinical diagnosis between age of 20 and 30 and have a known CAG repeat length.

Forty patients met criteria; 50%  males with 65% identified as white and 10% Hispanic or Latino. The average age of diagnosis was 28.9 years (range: 20-36). Initial presenting symptoms: 45% mood, 38% motor, and 18% cognitive symptoms. There was mixed motor presentations, including common choreiform syndrome and 20% akinetic rigid syndrome with dystonia. Average CAG repeat length was 49.8. Average initial Total Motor Score (TMS) was 31.3 with an average yearly decline of 3.2. Average initial Total Functional Capacity (TFC) was 9 with an average yearly decline of 0.8. There were 8 deaths, with average diagnosis-to-death of 14.4 years.

YOHD is a distinct subset of HD patients with mixed motor features of akinetic rigid syndrome seen in JHD and choreiform presentation seen in classic adult onset HD. Therefore, it is important to identify the unique combination of these clinical features to guide expectations around the disease course and appropriate treatment. This could be critical in future studies in Huntington’s disease.