YALE JOURNAL OF BIOLOGY AND MEDICINE 83 (2010), pp. 67-71. Copyright © 2010. CASE REPORT Expressive Aphasia as a Presentation of Encephalitis with Bartonella henselae Infection in an Immunocompetent Adult Carla B. Marienfeld, MDa*; Daniel B. DiCapua, MDb; Gordon K. Sze, MDc; and Jonathan M. Goldstein, MDb Departments of aPsychiatry, bNeurology, and cDiagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut Objective: To show the first clinically reported case of Cat Scratch Disease (CSD†) pre- senting as a focal neurologic deficit in an immunocompetent adult. Patient: 59-year-old male with a history of a previous stroke. Results: Examination showed an expressive aphasia, word substitution errors, and impaired repetition. A head CT and MRI showed no acute changes. The EEG findings were non-focal and did not show any epileptiform activity. The patient had a history of contact with stray kit- tens and previous axillary lymphadenopathy. Bartonella henselae serology titers were IgG positive 1:1024 (< 64) and IgM positive 1:20 (< 16). After antibiotic administration, the pa- tient’s symptoms and aphasia resolved. Conclusions: Focal presentations concerning for stroke or partial seizure activity may have underlying infectious etiology. We recommend consideration of CSD in the differential diag- nosis of any adult with a history of lymphadenopathy, fever, and recent contact with a cat who presents with neurologic complications. INTRODUCTION Bartonella henselae is the primary cause of Cat Scratch Disease (CSD) [1]. CSD occurs predominantly in the fall and winter months. Regional lymphadenopathy is noted in 85 percent of patients, most commonly in the neck, axilla, and inguinal region [2]. Typically, the disease is benign and self-limited with an associated fever usually occurring one to three weeks after a scratch, bite, or lick from a kitten [3,4]. In immunocompetent patients, the disease is usually self-limited with rare serious com- *To whom all correspondence should be addressed: Carla B Marienfeld, MD, Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT 06511; Tele: 203-974-7855; E-mail: carla.marienfeld@yale.edu. †Abbreviations: CSD, cat scratch disease. Keywords: Bartonella henselae, expressive aphasia, neurologic complications, en- cephalopathy, antibiotics 67