Optineurin mutation-associated language variant frontotemporal dementia

A right-handed woman in her early 50s presented with progressive language difficulties with visual and auditory hallucinations. Upper motor neuron signs were present without lower motor neuron signs, insufficient to make a diagnosis of amyotrophic lateral sclerosis (ALS). MRI showed bilateral superior temporal atrophy (right>left) and F-18 fluorodeoxyglucose-positron emmission tomography (FDG-PET) scan showed right temporal hypometabolism. Her clinical diagnosis was atypical or mixed language variant frontotemporal dementia (FTD) given the presence of agrammatism and phonemic intrusions. There was a family history of FTD and ALS. Genetic testing revealed a homozygous optineurin (OPTN) mutation. She experienced progressive auditory agnosias including musical agnosia and eventual mutism. A review of the literature reveals wide phenotypic variability of people with OPTN variants, emphasising the importance of genetic testing beyond that predicted by classical phenotypes.