Even experienced clinicians in endemic areas occasionally have difficulty diagnosing Rocky Mountain spotted fever (RMSF) in the early stages. Numerous pitfalls in diagnosis may test the acumen of even the best physicians. Rickettsia rickettsii, the cause of RMSF, has the potential to kill healthy persons of any age. Thus, physicians must be alert to the diagnosis and able to recognize usual and unusual clinical presentations. This is easier said than done.
Patients with RMSF may not give a history of tick bite in up to a third of cases. To make matters worse, rash occasionally may not occur in the first three to six days of illness. In other cases, rash may first appear in the terminal stages of illness or, rarely, not at all.1 Tongue in cheek, Westerman2 coined the term Rocky Mountain spotless fever to describe these patients and emphasized that waiting for a rash to