Frontotemporal dementia (FTD) is a clinical syndrome with a heterogeneous molecular basis. The past decade has seen the discovery of several new FTD‐causing genetic mutations and the identification of many of the relevant pathological proteins. The current neuropathological classification is based on the predominant protein abnormality and allows most cases of FTD to be placed into one of three broad molecular subgroups; frontotemporal lobar degeneration with tau, TDP‐43 or FET protein accumulation. This review will describe our current understanding of the molecular basis of FTD, focusing on insights gained from the study of human postmortem tissue, as well as some of the current controversies.

Most cases of FTD can be subclassified into one of three broad molecular subgroups based on the predominant protein that accumulates as pathological cellular inclusions. Understanding the associated pathogenic mechanisms and recognizing these FTD molecular subtypes in vivo will likely be crucial for the development and use of targeted therapies.

This article is part of the Frontotemporal Dementia special issue.