Ruptured Mycotic Cerebral Aneurysm Secondary to Disseminated Nocardiosis

We report a case of a ruptured mycotic cerebral aneurysm caused by Nocardia infection. A 22-year-old immunocompromised woman with adult-onset Still's disease developed a subarachnoid hemorrhage (SAH). Digital subtraction angiography revealed a small aneurysm at the M2-3 bifurcation of the right middle cerebral artery. Cardiac ultrasonography showed vegetation at the posterior cardiac wall, suspecting infective endocarditis (IE). Gram-positive filamentous bacteria were observed in the necrotic tissue surrounding the aneurysm obtained during trapping surgery. Long-term blood culture showed that the cause of her cerebral mycotic aneurysm was nocardiosis. A mycotic ruptured cerebral aneurysm is an important cause of SAH in immunocompromised patients. Early diagnosis of IE, detection of gram-positive rods by Gram staining, and long-term culture to identify the bacteria is crucial in diagnosing nocardiosis.