Cerebral amyloid angiopathy (CAA) is a common but often asymptomatic disease, characterized by the deposition of amyloid proteins within brain parenchyma and leptomeningeal-cortical vessels. It can occur as a sporadic disorder or accompany Alzheimer disease (AD). The usual presentation of CAA is spontaneous lobar hemorrhage, Unlike CAA, cerebral amyloid angiopathy-related inflammation (CAA-ri), a subtype of CAA, can show various presentations and responds to steroid (or immuno suppressive) treatment. We report a patient with mixed dementia who showed subacute progression in cognitive impairment and had a mass lesion on brain magnetic resonance imaging (MRI). The lesion was identified as CAA related inflammation and the cognitive status of the patient improved significantly after steroid treatment. In this case report, we aimed to emphasize that CAA-ri is one of the possible diagnoses that should be considered in demented patients with rapid cognitive deterioration and showing brain lesions resembling neoplasms on the MRI. Therefore, steroids or other immunosuppresive treatments, which may lead to a dramatic clinical improvement, could be administered without delay.
