ACTB -Related Dystonia-Deafness Syndrome with Functional Imaging Correlates: A Case Report

Dystonia-deafness syndrome (DDS) is a rare neurogenetic disorder with congenital sensorineural hearing loss and progressive dystonia linked to ACTB mutations. A 22-year-old man with congenital deafness and speech impairment presented with adolescent-onset tremors evolving to generalized dystonia, titubation, and gait disturbances. Magnetic resonance imaging of the brain was unremarkable. Fluorodeoxyglucose-positron emission tomography showed basal ganglia hypometabolism, with severely reduced uptake in the right putamen and caudate on Technetium-99m labeled TRODAT-1 Single Photon Emission Computed Tomography (TRODAT SPECT) imaging. A heterozygous pathogenic missense variant in ACTB gene (c.547C>T; p.Arg183Trp) with an additional heterozygous variant in VPS16 (c.1612C>A; p.Leu538Met) was identified. The ACTB variant explains core DDS features, whereas the coexisting VPS16 variant represents an additional finding of uncertain clinical significance. This case highlights the functional imaging abnormalities in ACTB -related DDS and emphasizes the value of multimodal imaging in the evaluation of genetically confirmed complex dystonia.