Consider genetic investigations in all of those with:• Suspected frontotemporal dementia• Dementia with onset <55 years of age• Family history compatible with a dementia-causing genetic variant;• Clinical features suggestive of Down Syndrome (mosaic cases) or rare single-gene forms of dementia.Genetic testing for dementia risk variants (including APOE4) or polygenic risk scores is not recommended. The gene discussed is APOE; the disease is Down syndrome.