Clinical and genetic profile of patients with dystonia: An experience from a tertiary neurology center from India

Background: The genetics of dystonia have varied across different ethnicities worldwide. Its significance has become more apparent with the advent of deep brain stimulation. Objective: To study the clinico-genetic profile of patients with probable genetic dystonia using whole exome sequencing (WES). Methods: A prospective, cross-sectional study was conducted from May 2021 to September 2022, enrolling patients with dystonia of presumed genetic etiology for WES. The study compared genetically-determined cases harboring pathogenic/likely-pathogenic variants (P/LP subgroup) with the presumed idiopathic or unsolved cases. Results: We recruited 65 patients (males, 69.2%) whose mean age of onset (AAO) and assessment were 25.0 +/- 16.6 and 31.7 +/- 15.2 years, respectively. Fifteen had pathogenic/likely-pathogenic variants (yield = 23.1%), 16 (24.6%) had variants of uncertain significance (VUS), 2 were heterozygous carriers while the remaining 32 cases tested negative (presumed idiopathic group). The P/LP subgroup had a significantly younger AAO (16.8 +/- 12.3 vs 31.3 +/- 17.0 years, p = 0.009), longer duration of illness (10.9 +/- 10.3 vs 4.8 +/- 4.3 years, p = 0.006), higher prevalence of generalized dystonia (n = 12, 80.0% vs n = 10, 31.3%, p = 0.004), lower-limb onset (n = 5, 33.3% vs n = 1, 3.1%, p = 0.009), higher motor (p = 0.035) and disability scores (p = 0.042). The classical DYT genes with pathogenic/likely pathogenic variants included 3 cases each of TOR1A, and KMT2B, and single cases each of SGCE, EIF2AK2, and VPS16. Non-DYT pathogenic/likely-pathogenic cases included PINK1, PANK2, CTSF, POLG, MICU1, and TSPOAP1. Conclusions: The yield of WES was 23.1% among cases of probable genetic dystonia. Pathogenic or likely pathogenic variants in TOR1A, KMT2B, and SGCE genes were commoner. The absence of family history emphasizes the importance of accurate assessment of clinical predictors before genetic testing.