• To highlight the clinical, radiographic, and histopathologic features that distinguish cerebral amyloid angiopathy (CAA-ri) from amyloid beta-related angiitis (ABRA), focusing on their differing patterns of vascular inflammation.

CAA-associated inflammatory disorders are rare, immune-mediated encephalopathies in older adults. Histopathology of CAA-ri shows non-destructive perivascular T-cell inflammation, while ABRA demonstrates destructive transmural vascular inflammation with mixed T-cell, macrophage, and B-cell infiltrates. MRI and current Boston Criteria 2.0 may suggest the diagnosis, but biopsy is required for confirmation. Early immunosuppression improves outcomes.

Case 1 (CAA-ri):
A 77-year-old woman with hypertension and hyperlipidemia developed several weeks of word-finding difficulty and cognitive decline, followed by acute aphasia and a generalized tonic-clonic seizure. MRI demonstrated left temporal and parieto-occipital vasogenic edema, lobar and punctate frontal microhemorrhages, and bilateral parieto-occipital superficial siderosis. CSF was unremarkable. Brain biopsy revealed perivascular chronic T-cell inflammation with beta-amyloid deposition. She was treated with IV methylprednisolone, oral prednisone taper, long-term mycophenolate, and levetiracetam. At one year, she returned to her baseline cognitive and functional status.

Case 2 (ABRA):
An 84-year-old woman with hypertension and osteopenia had a two-year history of subtle memory decline followed by acute onset of gait difficulty, bilateral leg weakness, and confusion over 48 hours. Exam revealed fluctuating lower extremity strength, abulia, and word-finding difficulty. MRI showed bilateral frontal and parietal edema, cortical subarachnoid hemorrhage, leptomeningeal enhancement, and superficial siderosis. CSF demonstrated lymphocytic pleocytosis with elevated protein. Biopsy revealed destructive vascular inflammation with T-cells, macrophages, B-cell aggregates, and beta-amyloid deposition. She was treated with IV methylprednisolone, oral prednisone taper, mycophenolate, and levetiracetam. Neurological deficits stabilized with recovery of gait, though sleep and mood disturbances persisted.

CAA-ri and ABRA share similar clinical and imaging features and tend to respond well to immunosuppressive therapy. Histopathology distinguishes the two entities. Recognition, biopsy, and early immunosuppression are essential for optimal outcomes.