Clinical, imaging and genetic profile of KMT2B-related dystonia: a review of published cases.

KMT2B gene variants are associated with early-onset generalised dystonia. The geographical influence on genotype-phenotype correlations remain incompletely characterized. To compare the clinical, imaging, and genetic profiles of Asian and European/American cohorts with KMT2B-related dystonia and study the genotype-phenotype correlations. We report a patient with KMT2B-related dystonia from our centre and present a comparative analysis of the clinical, imaging, and genetic profiles of published cases from Asian countries (including India) and European countries/America. There were 53 patients in the Asian and 125 in the European/American cohorts. Asian cohort patients had male predominance and a higher frequency of generalized dystonia, whereas the European/American cohort had female predominance, more segmental dystonia, higher rates of intellectual disability, psychiatric manifestations, status dystonicus, and pallidal hypointensity. There were 112 patients with protein truncating variant and 66 with missense variants. Protein-truncating variants were associated with more severe phenotypes, including cervical/laryngeal dystonia, dysmorphism, microcephaly, endocrinopathies, and wheelchair dependence, whereas missense variants showed later onset and more frequent psychiatric features. There were phenotypic and imaging differences in KMT2B-related dystonia across Asian and European/American cohorts. The European/American cohort had higher rates of segmental dystonia, intellectual disability, psychiatric manifestations, status dystonicus and and pallidal hypointensity. Protein-truncating variants had frequent manifestations of dysmorphic facial features, microcephaly, endocrinopathies, wheelchair dependence, and pallidal hypointensity as compared to the missense variants.