An Abnormal Presentation of Rocky Mountain Spotted Fever: A Case Report

Abstract

The intracellular coccobacilli Rickettsia rickettsii causes Rocky Mountain Spotted Fever, a potentially fatal illness. This bacterium is transmitted to humans through a tick vector. Patients classically present with a triad of symptoms, including fever, headache, and a rash that begins on the extremities and spreads proximally to the trunk. Diagnosis of this disease can prove difficult when patients have unusual symptoms, such as hypertensive crisis. In this case report, we present a 29-year-old male who arrived at the emergency room with altered mental status and a hypertensive crisis after his family reported one week of changes in his behavior. The patient had no evidence of ticks, tick bites, fever, or rash. Positive findings in the emergency room included a WBC of 14.9 × 109. All other physical exams, imaging, and laboratory findings were non-contributory. The patient was promptly given IV hydralazine to control his blood pressure and empiric IV ceftriaxone for potential infection, and he was admitted for observation. Over the course of three days, WBC levels decreased, and his altered mental status improved. On day 3, the patient remembered a tick crawling across his hand, and this prompted the ordering of immunoglobulin levels for tick-borne illnesses. IgM for RMSF was positive. This case presentation illustrates the need for clinicians to keep the potential diagnosis of RMSF high on the differential, even in the presence of a paucity of symptoms, as prompt treatment with doxycycline can be lifesaving. This case may also be one of the first reported in the literature of hypertension being a symptom of Rocky Mountain Spotted Fever. It is plausible, however, that this patient's hypertension was due to an acute stress response.

Keywords: altered mental state; confusion; hypertension; rocky mountain spotted fever; tick bite; unusual presentation.

Figure 1. Hospital course timeline including clinical findings, laboratory findings, and treatment. The timeline begins seven days prior to admission and the three day hospital stay.

AMS: altered mental status; WBC: white blood cells (normal WBC reference range: 4.5 x 10⁹/L to 10.1 x 10⁹/L); CSF: cerebrospinal fluid; IV: intravenous; IM: intramuscular; IgM: immunoglobulin M; RMSF: Rocky Mountain Spotted Fever.