Primary progressive aphasia (PPA), initially described by Mesulam, is a syndrome of progressive deterioration of language, occurring in the presenium. Several classifications have been proposed, but the most useful one distinguishes non fluent and fluent forms of PPA. Both begin by anomia. In non fluent PPA, there is a progressive reduction of language, sometimes with aggramatism and articulatory impairment, but without impairment of comprehension. Fluent PPA is characterized by preserved fluency with severe impairment of single word comprehension. It is frequently confounded with semantic dementia (SD), but some observations can be differentiated from SD. After several years, all patients become mute, and most of them develop dementia, usually of frontal lobe type. The syndrome of PPA is due to neurodegenerative brain pathology affecting mostly the perisylvian regions of the left hemisphere. In most cases, no Alzheimer type pathology was found in the brain, but tauopathy (mainly in non fluent PPA) or motor neuron disease type pathology - tau negative ubiquitin inclusions (mainly in fluent PPA). However, Alzheimer type pathology was found in a substantial number of cases.