Abstract Posterior cortical atrophy (PCA) is a visual-cognitive syndrome caused by Creutzfeldt-Jakob disease (CJD), Alzheimer's disease (AD), or subcortical gliosis. We report a case of posterior cortical atrophy unique in (1) comprehensive documentation of clinical, radiologic, electroencephalograph, metabolic and histopathologic findings, (2) repeated clinical and laboratory assessment, and (3) establishment of unique occipital subcortical gliosis in a patient with AD. Clinical manifestations of PCA caused by AD included visual agnosia, cortical blindness, optic apraxla, delusions, hallucinations, agitation, depression, amnestic deficit, Wernicke's aphasia, acalculia, and left/right disorientation. Posterior cortical atrophy produced by AD can be demonstrated on magnetic resonance imaging, positron emission tomography, and electroencephalography; determination of the etiology requires tissue examination. Autopsy-diagnosed cases in the literature document PCA due to CJD and AD with equal frequency.