Unraveling the genetic architecture of non-Huntington chorea: a biobank-scale study of rare variants and repeat expansions.

Chorea can arise from genetic, metabolic, pharmacologic, and autoimmune causes. In clinical practice, however, non-genetic causes are rare. The most common genetic cause is a CAG repeat expansion in HTT, leading to Huntington's disease (HD). Beyond HD, systematic studies have been lacking and many individuals with non-HD chorea remain without a molecular diagnosis. We conducted whole-exome and genome sequencing analysis on 190 non-HD chorea cases, leveraging data from the All of Us Research Program (n = 134), UK Biobank (n = 26), and a clinically ascertained multicenter Spanish cohort recruited by the Spanish Study Group for Genetics of Chorea (SSGGC) (n = 30). Variant calling was performed without pre-filtering based on a disease or gene list, and variants were clinically contextualized using OMIM, ClinVar, and in silico predictions. We identified thirteen protein-altering variants, including six previously described as pathogenic or likely pathogenic. Notably, we identified a pathogenic JPH3 expansion in a patient of Black race and c9orf72 expansions in individuals of European and South Asian ancestry. These findings explained 23% of cases in the SSGGC, 12% in UK Biobank, and 4% in All of Us. Our results broaden the genetic architecture of non-HD chorea and highlight the value of multi-ancestry genomic approaches for rare movement disorders.