and the Harry S. Truman Memorial Veterans Affairs Hospital, Columbia, Missouri; and the McFarland Clinic, Ames, Iowa Since 1989~we have confirmed the diagnosis of human ehrlichiosis in 57 patients. Although routine radiological studies of the central nervous system (CNS) or analyses of cerebrospinal fluid (CSF) samples were not done for these patients, primary care physicians detected symptoms or signs that prompted them to perform such studies. CSF samples were examined for 15 of the 57

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... s. Findings in eight of the 15 CSF samples were abnormal, and the most common abnormalities were lymphocytic pleocytosis and elevated protein levels. A search of the English-language literature revealed 21 additional cases in which CSF examinations were performed; in 13 of these cases, CSF findings were abnormal. The most common clinical finding that predicted CSF abnormalities was a change in mental status. A total of 14 patients underwent computerized tomographic studies, and none of these studies showed abnormalities. Four (19%) of the 21 patients with CNS manifestations of ehrlichiosis and abnormal CSF findings died.