Objective: To present a case of posterior cortical atrophy (PCA) that was proven not to be Alzheimer disease (AD). PCA is rare and poorly understood but is a distinctive dementia syndrome thought to be caused by atypical Alzheimer disease (AD). The results presented suggest a unique yet to be defined neurodegenerative disease process. Method: A 55-year-old female presented with a 4 year history of absentmindedness and visuospatial symptoms. Diagnostic included serial MRI, serial neuropsychological studies, PET and CSF ADMark. Profound posterior cortical metabolic inactivity and occipital/posterior parietal atrophy characterized imaging. The CSF was negative for AD AB42/tau biomarkers. Results: Serial neuropsychological studies demonstrated psychometric decline over the observation interval and a neurobehavioral syndrome characterized by features of Balint's syndrome with oculomotor apraxia, optic ataxia, and simultagnosia. Profound visuospatial deficits where noted on Block Design (SS = 2), Trail Making Test part A (discontinued because “dot appeared and disappeared”), Clock Drawing test (0/4), piecemeal description on Boston Cookie Theft picture with qualitative complaints “it is like too many thing are going on (visually) at once.” Other cognitive function was relatively preserved. Conclusion(s): PCA is a rare distinctive dementia syndrome that is thought to be atypical AD. Our case was a classic presentation of Benson's (1988) original description. Our case uniquely contributes to the literature as the biomarkers for AD were negative. It is likely that this case would fall into the category “dementia lacking specific histological features.” Accurate classification of such cases for further study will ultimately contribute to better understanding of neurodegenerative diseases.