Case Report: Dynamic Fusiform MCA Aneurysm in Culture‐Negative Endocarditis and DRESS Syndrome: Infectious Aneurysm or Superimposed Immuno‐Inflammatory Arteriopathy?

A 37‐year‐old woman with reported beta‐thalassemia minor presented with right Sylvian subarachnoid hemorrhage after several weeks of fever of unknown origin while receiving antibiotic therapy. Initial catheter angiography demonstrated right middle cerebral artery (MCA) branch occlusion without aneurysm; repeat imaging 1 week later demonstrated a dynamic distal right MCA fusiform aneurysm with circumferential vessel wall enhancement and adjacent cerebritis. Echocardiography revealed aortic valve vegetation, but blood cultures, plasma microbial cell‐free DNA testing, and CSF metagenomics were negative throughout her hospitalization. The cerebral aneurysm was managed as a culture‐negative infectious aneurysm, but parent vessel sacrifice was deferred because functional MRI demonstrated bihemispheric language representation and there was a pre‐existing adjacent MCA branch occlusion. Her course was complicated by DRESS syndrome (suspected culprit: vancomycin), accompanied by cervical lymph node histiocytic necrotizing lymphadenitis with Kikuchi‐Fujimoto‐disease‐like features, prompting immunosuppression. Following DRESS‐directed corticosteroid therapy, follow‐up brain MRI and MR angiography (MRA) showed inflammatory changes and aneurysm remodeling and improvement in adjacent cerebral edema. This case illustrates the diagnostic and management overlap between culture‐negative infectious arteritis and a possible superimposed immuno‐inflammatory arteriopathy in the setting of DRESS‐associated hyperinflammation, highlighting the need for serial brain MRI and MRA, MR vessel‐wall imaging, and multidisciplinary decision‐making.