Frontotemporal lobar degeneration

Frontotemporal lobar degeneration (FTLD) is one of the most common causes of early-onset dementia and presents with early social–emotional–behavioural and/or language changes that can be accompanied by a pyramidal or extrapyramidal motor disorder. About 20–25% of individuals with FTLD are estimated to carry a mutation associated with a specific FTLD pathology. The discovery of these mutations has led to important advances in potentially disease-modifying treatments that aim to slow progression or delay disease onset and has improved understanding of brain functioning. In both mutation carriers and those with sporadic disease, the most common underlying diagnoses are linked to neuronal and glial inclusions containing tau (FTLD-tau) or TDP-43 (FTLD-TDP), although 5–10% of patients may have inclusions containing proteins from the FUS–Ewing sarcoma–TAF15 family (FTLD-FET). Biomarkers definitively identifying specific pathological entities in sporadic disease have been elusive, which has impeded development of disease-modifying treatments. Nevertheless, disease-monitoring biofluid and imaging biomarkers are becoming increasingly sophisticated and are likely to serve as useful measures of treatment response during trials of disease-modifying treatments. Symptomatic trials using novel approaches such as transcranial direct current stimulation are also beginning to show promise. Frontotemporal lobar degeneration is one of the most common causes of early-onset dementia. This Primer summarizes the epidemiology, pathophysiology, diagnosis, and treatment of frontotemporal dementia and discusses how this disorder affects patients’ quality of life.