Mystery Case: Eccentric target sign in CNS toxoplasmosis

Abstract

A 61-year-old man with myasthenia gravis who previously underwent post-thymectomy radiotherapy for a metastatic thymoma presented with altered mental status. Examination revealed papilledema and frontoexecutive dysfunction.Brain MRI disclosed rim-enhancing lesions with the eccentric target sign pathognomonic for neurotoxoplasmosis, 1 supported by magnetic resonance spectroscopy (figure 1). Brain biopsy confirmed the presence of Toxoplasma gondii tachyzoites (figure 2). Absent B cells, low CD4 + and CD8 + counts, hypogammaglobulinemia, and a HIV-negative status led to the diagnosis of Good syndrome. Treatment with pyrimethamine-clindamycin resulted in mild improvement.Neurotoxoplasmosis is a rare opportunistic infection in HIV-negative patients with thymoma. 2 Early recognition and prompt immunologic workup are warranted.