A 51-Year-Old Woman With Subarachnoid Hemorrhage and Secondary Central Nervous System Vasculitis With Progression to Diffuse, Serpiginous Dolichoectasia.

A 51-year-old woman presented with acute onset of a severe headache, and was found to have diffuse subarachnoid hemorrhage with prominent cisternal and left cortical convexity blood on head computed tomography. The first 2 conventional angiograms were negative for aneurysm, but a third angiogram revealed a mycotic aneurysm of a distal left middle cerebral artery branch. Brain biopsy, associated with clipping of the aneurysm, demonstrated pathology consistent with vasculitis. Over the course of a month, she developed diffuse, serpiginous dolichoectasia of the cerebral arteries. Further investigation into the cause of vasculitis supported a diagnosis of either eosinophilic granulomatosis with polyangiitis (EGPA) or IgG4-Related Disease (IgG4-RD). The following clinical pathologic conference discusses the diagnostic challenges in discriminating between these 2 diseases, particularly in the setting of secondary angiitis of the central nervous system.