Probable cerebral amyloid angiopathy - related inflammation in a 32-year-old woman with down syndrome

Inflammatory cerebral amyloid angiopathy (CAA-RI) is a variant of CAA, rarely seen in young individuals with Down syndrome (DS). We describe a 32-year-old female with DS who developed a systemic inflammatory state followed by acute neurological symptoms, including seizures and hemiparesis. Brain MRI disclosed asymmetric T2/FLAIR hyperintensities with leptomeningeal enhancement and focal superficial siderosis on susceptibility-weighted imaging, without microbleeds; cerebrospinal fluid showed marked inflammation. After partial improvement with corticosteroids, rituximab was started due to persistent symptoms. This case highlights CAA-RI as a cause of acute decline in DS and supports the use of rituximab in refractory cases.