Objective: To report and describe two novel missense mutations in KMT2B identified in two dystonia patients from China.

Background: Recently, two independent groups have reported mutations in a newly identified gene, lysine methyltransferase 2B (KMT2B) in patients with early-onset dystonia.

Methods: We sequenced the exomes of two dystonia patients from China. Bioinformatics analyses were conducted to select candidate causal variants in described dystonia-mutated genes. After cosegregation testing, the effects of identified variants were classified according to the American College of Medical Genetics and Genomics (ACMG) standards and guidelines.

Results: Two novel missense variants in KMT2B were identified (p.Arg152Trp, p.Gly1098Arg). Both two missense vatiants were predicted to be disease-causing by SIFT, PolyPhen-2 and MutationTaster, and were absent from population-based databases (1000 genomes and ExAc). The associated phenotype comprised adolescence-onset segmental isolated dystonia with prominent speech impairment in the first patient and postural tremor of hands in the second patient, which was different from the reported phenotypes.

Conclusions: We reported two novel missense variants in KMT2B, broadening the mutation spectrum and phenotype spectrum of KMT2B.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/novel-missense-variants-in-kmt2b-in-segmental-dystonia/