Clasificación clínica y biomolecular de las demencias frontotemporales. Revisión de la bibliografía

The term 'frontotemporal lobar dementia' (FTLD) covers a group of neurodegenerative diseases that are very heterogeneous in their clinical expression, genetic component and histopathological features, and this has traditionally made it difficult to study and classify them. Patients usually present a progressive change in their behaviour associated with language disorders and loss of memory, which constitutes the second most important cause of dementia in persons under the age of 65. The most significant characteristic at the histopathological level is the presence of abnormal aggregates or accumulations of proteins in neurons or glial cells; their identification has, on the one hand, helped further our knowledge of the pathogenic mechanisms and, on the other hand, has allowed this type of dementia to be classified.In the last two decades a remarkable amount of progress has been made in our knowledge of this group of diseases, thanks to the genetic advances related to the discovery of the MAPT gene and the progranulin gene, as well as their mutations, which are responsible for a high percentage of cases of hereditary FTLD. Likewise, the development of new immunohistochemical techniques has made it possible to characterise some abnormal proteins, such as the protein TDP-43, as the main component of the neuronal inclusions in tau-negative FTLD. All this has led to a new classification of the FTLD. This work includes a thorough review of said advances and the possible clinical, histological, genetic and biomolecular correlations of the different subtypes of FTLD are also considered.