Genetic Counseling for Frontotemporal Dementias

Abstract

Frontotemporal dementia (FTD) is an umbrella term for a heterogeneous group of neurodegenerative disorders that are characterized by changes in cognition, language, personality, and social functioning. Approximately 40% of individuals with FTD have a family history of dementia, but less than 10% have a clear autosomal dominant pattern of inheritance. However, establishing a clear mode of inheritance in FTD is complicated by clinical heterogeneity, variable expression, phenocopies, misdiagnosis, early death due to other causes, missing medical records, and lost family histories. Mutations in the microtubule-associated protein tau and progranulin genes have been reported in the majority of hereditary cases, making genetic testing of at-risk individuals possible. The first step in counseling a family with a history of FTD is to take a comprehensive family history with confirmation of any diagnosis in a family member with medical records to the extent possible. If the pedigree analysis suggests an autosomal dominant pattern of inheritance, genetic testing of an affected relative may be offered to the family to determine if a mutation is present. If a mutation is found, relatives interested in pursuing genetic testing should be referred to a genetic counselor familiar with genetic testing for neurodegenerative disorders. Predictive testing of unaffected and at-risk relatives should only be offered in the context of a comprehensive genetic counseling protocol offering pre- and post-test counseling and support. One survey of at-risk individuals in a large family with FTD found that 50% were interested in testing. In one study actually offering genetic testing for FTD, the rate of uptake of testing was only 8.4%. A more recent study estimated the uptake for testing for FTD to be somewhere between 7% and 17% and attributed the low uptake to family resistance to testing. While genetic testing may be appropriate for some families with Alzheimer's disease and FTD, uptake of testing may be expected to be low.