Supplementary Material for: A case of severe cerebral amyloid angiopathy-related inflammation (CAA-ri) in a 81-year-old woman with rapid cognitive decline

Introduction Cerebral amyloid angiopathy (CAA) is a vasculopathy characterized by amyloid-beta (Aβ) deposition in the walls of the leptomeningeal and cortical blood vessels. In a minority of patients with CAA, presence of amyloid-beta (Aβ) deposition triggers an autoimmune inflammatory reaction, referred to as CAA-related inflammation (CAA-RI). It can present in two forms, either as perivascular CAA-related inflammation (CAA-ri) or as Aβ-related angiitis (ABRA). The mechanism underlying CAA-RI remains unclear. Symptoms are subacute mental disorders and behavioral or cognitive changes, headaches, seizures and focal neurological deficits. Most commonly, CAA-ri is a monophasic illness. Relapses occur often years after the initial presentation and are correlated with corticosteroid tapering or immunosuppression cessation. Treatment is often prolonged, but effective. We present a rare and instructive case with CAA-ri characterized by rapid cognitive decline, therapy resistance and fatal outcome and discuss current literature. Case presentation We describe a case of an 81-year-old female who presented with progressive confusion, behaviour alterations, recurrent falls and vomiting since two weeks. There was a rapid cognitive decline and fatal outcome. The diagnosis of a probable CAA-ri was made based on the clinical presentation and brain MR imaging. To allow long-term corticosteroid replacement, azathioprine was initiated for second-line immunosuppression. Conclusion This case report of CAA-ri describes the diagnostic and therapeutic challenges in an elderly patient with rapid cognitive decline. It highlights the severe nature of the condition, the limitations of available treatments and the importance of early recognition based on the diagnostic criteria and MR imaging and start of the therapy, while acknowledging that outcomes may remain poor despite intervention.