A KMT2B Frameshift Variant Causing Focal Dystonia Restricted to the Oromandibular Region After Long-Term Follow-up

Abstract

<i>KMT2B</i>-linked dystonia (DYT-<i>KMT2B</i>) is a childhood-onset dystonia syndrome typically beginning in the lower limbs and progressing caudocranially to affect the upper limbs with eventual prominent craniocervical involvement. Despite its recent recognition, it now appears to be one of the more common monogenic causes of dystonia syndromes. Here, we present an atypical case of DYT-<i>KMT2B</i> with oromandibular dystonia as the presenting feature, which remained restricted to this region three decades after symptom onset. This appears to be the first reported case of DYT-<i>KMT2B</i> from Southeast Asia and provides further supporting evidence for the pathogenic impact of the <i>KMT2B</i> c.6210_6213delTGAG variant.