Progressive prosopagnosia at a very early stage of frontotemporal lobar degeneration

Background: The present paper describes a patient with a right temporal lobe variant (RTLV) of frontotemporal lobar degeneration (FTLD). Methods: The study was undertaken when the patient was completely independent in her environment and had not complained of any cognitive problems. Results: Under general neuropsychological assessment, the patient showed no notable deficit other than a difficulty in recognizing famous people by looking at photographs of their faces. Subsequent in‐depth evaluation indicated prosopagnosia: the patient presented with an impaired ability to recognize the faces of famous people and family members, whereas her visuospatial abilities were intact. Because the patient was able to recognize familiar people by their voices, the impairment was not a general loss of knowledge about people, but an inability to access this knowledge from visual stimuli (i.e. via the visual modality). The patient also exhibited a ‘within‐category’ learning deficit; however, her ability to learn from ‘across‐category’ visual stimuli remained intact. Conclusions: Overall, the results of the present study support the proposed model of RTLV of FTLD, where the first sign would be the disruption of face recognition components, leading to a selective form of associative prosopagnosia. Further, the co‐occurrence of face and ‘within‐category’ object learning deficits favor an interpretation in which a more generalized deficit occurs ‘earlier’ in the sequence of events associated with the object recognition process.