Rocky Mountain spotless fever: a dilemma for the clinician.

Failure of the characteristic rash to develop during the course of illness in Rocky Mountain spotted fever may lead to the delay or failure of diagnosis and may result in fetal encephalopathic illness with disseminated vascular injury. Four patients are described herein in whom a rash failed to develop and the diagnosis was initially incorrect. Each patient was seen at least once before hospital admission by a physician and given ineffective antibiotic therapy, resulting in fatal complications. Besides the failure of the rash to develop, the lack of any specific diagnostic test that is useful during the acute illness represents a major difficulty for the physician in making the diagnosis before the patient's death. Any adult in an endemic geographic area who is initially seen with an undifferentiated acute febrile illness in which headache and myalgias are prominent should be considered for treatment with tetracycline unless otherwise contraindicated.