A 71-year-old man with no significant medical history presented with acute slurred speech, left facial droop, and left hand paresthesia. Head CT showed small intraparenchymal hemorrhage (IPH) in left frontal and right parietal lobes, plus subarachnoid hemorrhage (SAH) throughout right parieto-temporal sulci. MRI revealed mild vasogenic edema surrounding the hemorrhages, leptomeningeal enhancement in right parietotemporal sulci, and numerous cortical microbleeds. CSF was xanthochromic with mildly elevated protein but without pleocytosis. CTA and MRI vessel wall imaging were unremarkable. Although he remained clinically stable, repeat MRI one month later showed new SAH and microbleeds throughout right hemispheres and a new left frontal IPH. The rapidly worsening hemorrhage prompted a biopsy, which revealed amyloid deposition in leptomeningeal and intraparenchymal medium-sized arteries with transmural   granulomatous inflammation, consistent with ABRA. High-dose Prednisone was initiated. However, one month later he developed confusion, brain MRI showed multiple foci of new punctate infarcts within right frontoparietal lobes. Monthly cyclophosphamide infusion was initiated after IV methylprednisolone induction. He achieved remission with serial MRIs showed no new infarcts or hemorrhage after two cycles of cyclophosphamide infusion.  

We report a case of ABRA confirmed by biopsy. Features such as older age, multifocal hemorrhages with punctate infarcts, cortical microhemorrhages, and leptomeningeal enhancement should raise suspicion for ABRA. Diagnosis requires biopsy showing vessel wall amyloid deposits with transmural inflammation. Prompt immunotherapy is essential due to rapid progression, and remission in ABRA often requires combined corticosteroid and cyclophosphamide therapy.