Frontotemporal lobar degeneration (FTLD) comprises a highly heterogeneous group of disorders clinically associated with behavioral and personality changes, language impairment and deficits in executive functioning and pathologically associated with degeneration of frontal and temporal lobes. Some patients present with motor symptoms including amyotrophic lateral sclerosis. Genetic research over the past two decades in FTLD families led to the identification of three common FTLD genes (microtubule associated protein tau, progranulin and chromosome 9 open reading frame 72) and a small number of rare FTLD genes, explaining the disease in almost all autosomal dominant FTLD families but only a minority of apparently sporadic patients or patients in whom the family history is less clear. Identification of additional FTLD (risk) genes is therefore highly anticipated, especially with the emerging use of next-generation sequencing. Common variants in the transmembrane protein 106 B were identified as a genetic risk factor of FTLD and disease modifier in patients with known mutations. This review summarizes for each FTLD gene what we know about the type and frequency of mutations, their associated clinical and pathological features and potential disease mechanisms and we provide an overview of emerging disease pathways encompassing multiple FTLD genes. We further discuss how FTLD specific issues such as disease heterogeneity, the presence of an unclear family history and the possible role of an oligogenic basis of FTLD can pose challenges for future FTLD gene identification and risk assessment of specific variants. Finally, we highlight emerging clinical, genetic and translational research opportunities that lie ahead. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.