Fourth nerve palsy caused by Ehrlichia chaffeensis.

Two human ehrlichioses occur in the United States: human monocytic ehrlichiosis (HME), which is caused by Ehrlichia chaffeensis that infects mononuclear phagocytes in blood and tissue, and human granulocytic ehrlichiosis (HGE), an infection of granulocytes that is caused by a similar but phylogenetically distinct organism. The clinical features of both forms of human ehrlichiosis are identical and include nonspecific constitutional manifestations, such as fever, headache, malaise, nausea, vomiting, myalgia, and anorexia; however, rare patients develop neurologic symptoms and signs. Few cases of human ehrlichiosis have been described in detail, and focal neurologic deficits have only rarely been reported in such cases. We describe a patient with HME who developed a trochlear nerve paresis associated with evidence of lymphocytic meningitis during the course of her illness. We believe this to be the first well-documented case of a focal neurologic complication of human ehrlichiosis.