Meningoencephalitis as a major manifestation of Rocky Mountain spotted fever.

Although our two patients had very different courses, both illustrate the gravity of rickettsial meningoencephalitis. The presence of neurologic signs and symptoms is ominous and should be recognized as a possible manifestation of Rocky Mountain spotted fever. A high index of suspicion for RMSF needs to be maintained in patients with an acute febrile illness, especially in endemic areas, even during periods other than "tick season," and in patients without a rash.