When is inheritance a factor in Alzheimer's?
QWhat is the inheritance of Alzheimer's disease, and if genetic screening is available for single gene inheritance, who should be screened and where?
AThe vast majority of cases of Alzheimer's disease, the most common form of dementia in older people, do not have any strong evidence for inheritance. Only in rare cases is there any indication of a genetic cause, and these probably represent only 1 per cent of the total cases seen.
Inherited forms of Alzheimer's disease are almost invariably of early onset, with presentation at under 65 years of age.
Only in about 5 per cent of such cases will there be a genetic cause, with the primary indication being evidence of family history, often with a similar or identical disease in the previous generation.
Patients will present with an onset frequently in their 40s or 50s and show a relatively rapid progression of the illness, with additional neurological signs such as myoclonus, with other family members showing comparable age at onset and clinical features.
Genetic screening for these families is available at specialist centres, but should only be undertaken after referral of family members to the local regional genetics service for counselling.
Dr Christopher Morris is senior lecturer at MRC-University of Newcastle upon Tyne centre for clinical brain ageing