CADASIL presenting with a behavioural variant frontotemporal dementia phenotype

The behavioural variant of frontotemporal dementia (bvFTD) is characterised by personality change with a decline in cognition. We describe two patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukencephalopathy (CADASIL) who presented with behavioural phenotypes similar to bvFTD. The first patient presented with progressive personality and behavioural change, had florid white matter hyperintensity, and had a novel missense mutation C366W in exon 7 of the Notch3 gene. The second patient presented with progressive memory impairment and marked personality changes after a transient ischaemic attack. In this second patient, the radiological features were subtle and only the family history of stroke prompted testing for CADASIL using Notch3 genotyping. We present these patients to demonstrate that CADASIL may mimic bvFTD, with little clinical or radiological evidence to distinguish the two. CADASIL may be an under-recognised diagnosis in apparent bvFTD. Screening Notch3 in a substantial and unselected cohort of frontotemporal dementia patients might be appropriate to investigate this possibility.