Abstract DP395: A Diagnostic Dilemma: A Case of Amyloid Beta-Related Angiitis Mimicking Posterior Reversible Encephalopathy Syndrome

Introduction: Amyloid-beta related angiitis (ABRA) is a rare central nervous system (CNS) vasculitis characterized by widespread vessel involvement with transmural, granulomatous infiltrates. Its clinical presentation can mimic conditions such as primary CNS vasculitis, infections, and malignancies, making diagnosis challenging. This report presents a diagnostically difficult case of ABRA with MRI findings overlapping with atypical PRES. Case Presentation: A 72 years-old man with history of adrenal insufficiency and rheumatoid arthritis, on chronic immunosuppression with methotrexate and steroids came hypertensive (SBP at 190s) with dull frontal headache, gait instability, and blurred vision over 2 months. His examinations on initial encounters were unremarkable. Brain MRI revealed multiple foci of diffusion hyperintensity in the bilateral (right > left) posterior parietal, temporal, and occipital lobes, with intermediate-to-low ADC signal, susceptibility, and enhancement. Vessel imaging was unremarkable. Initial differentials included atypical PRES, subacute infarct, and infection. Despite supportive management, the patient showed no improvement, and new MRI findings demonstrated increased diffusion hyperintensity with patchy enhancement in the basal ganglia and corona radiata. This prompted further investigation into vasculitis or CNS lymphoma. Extensive serum testing for vasculitis was unremarkable, revealing only mildly elevated CRP and erythrocyte sedimentation rate. CSF results showed 17 WBCs, normal glucose and elevated protein at 99. CSF culture and flow cytometry were negative. Neurosurgical biopsy showed amyloid deposition in the leptomeningeal and cortical vessels with granulomatous inflammation and necrosis, consistent with ABRA. The patient received a high dose Solumedrol and a single dose of Rituximab, resulting in rapid clinical improvement. He was discharged on 60mg oral prednisone with plan for gradual tapering. Conclusion: There’s no established clinical correlation between ABRA and PRES and can have overlapping radiological findings such as diffusion hyperintensity, enhancement and microhemorrhages. For suspected atypical features, persistent deficit or new imaging findings despite optimization warrants further work-up as distinguishing entities is crucial, as the management strategies defer significantly.