Rocky Mountain spotted fever

A 36-year-old man presented to the outpatient clinic reporting an approximate 3-day history of fever and progressively worsening rash. The fever had peaked at 103.5 °F, and improved with ibuprofen, but the rash—which started on his hands and ankles before moving centrally toward his chest—did not improve with any interventions. The patient also reported fatigue, body aches, and headache. He denied sick contacts and stated that he had returned home from hiking with friends in the Smoky Mountains about a week and a half earlier, with none of the friends with whom he had traveled reporting any illness. The patient's vital signs were temperature, 100.0 °F (with ibuprofen use); heart rate, 107 beats/min; respirations, 19 breaths/min; and BP, 118/84 mm Hg. Physical examination revealed a purple, macular rash over the patient's bilateral upper and lower extremities, extending proximally to the trunk. GENERAL FEATURES Rocky Mountain spotted fever (RMSF) is a tick-borne disease caused by the Gram-negative, obligate intracellular bacterium Rickettsia rickettsii. Transmitted by several species of tick including American dog tick, Rocky Mountain wood tick, and Brown dog tick Curable but potentially lethal disease ranging from mild to fulminant illness Can cause severe multiorgan dysfunction and death if untreated Occurs throughout the United States (most prevalent in southeastern/south-central states), Canada, Mexico, Central America, and South America Can occur in any month of the year but most cases in the United States are reported from May to September Incidence has been steadily increasing since 2000, with a threefold increase from 2010 to 2018 and a current average of approximately 500 cases per year Incidence is higher in children younger than age 10 years; however, mortality is higher in the elderly, specifically starting at age 60 years and older. Patients infected with Rickettsia rickettsii become symptomatic after 2 to 14 days (average 5 to 7 days). CLINICAL FEATURES Rickettsial infection leads to direct vascular injury. Endothelial cells produce prostaglandins that contribute to increased vascular permeability. The host response can lead to a variety of clinical manifestations. Early symptoms of RMSF are nonspecific and include fever, headache (can be severe), malaise, myalgia, and arthralgia; a rash may develop later in the course. Nausea, vomiting, abdominal pain, cough, and hard palate lesions may also occur. The hallmark of RMSF is a blanching, nonpruritic, erythematous rash with macules, developing between days 2 and 6 of fever, that progresses from macular to maculopapular and eventually petechial. The rash typically begins on the ankles and wrists, spreading centrally to the arms, legs, and trunk over the next 2 to 3 days. Involvement of the palms and soles is characteristic. Once petechiae develop, the rash no longer blanches. Characteristic rash occurs in approximately 90% of patients; however, only about half exhibit the rash at day 3 of fever and other symptoms. Onset of symptoms may be abrupt or gradual. In fulminant cases, death may occur as early as within 5 days of illness onset. Increased vascular permeability and thrombocytopenia contribute to more severe complications, including encephalitis, noncardiogenic pulmonary edema, acute respiratory distress syndrome, cardiac arrhythmias, coagulopathy, gastrointestinal bleeding, skin necrosis, seizures, and death. Box 1DIAGNOSIS A presumptive diagnosis is made based on history and characteristic clinical findings in an appropriate epidemiologic setting. RMSF should be suspected in patients from an endemic area (or who have visited one within the past 14 days) who: ♦ Present in spring or summer with fever and at least one of the following: ◊ Rash ◊ Headache ◊ Constitutional symptoms ◊ Laboratory abnormalities ♦ AND have a known tick bite or exposure to environments where ticks are present. Clinical diagnosis is confirmed through serologic testing. Serologic testing is not helpful during the first 5 days of symptoms because antibodies are typically not yet detectable. Indirect immunofluorescence assay is the serologic test of choice. IgM and IgG antibodies generally appear 7 to 10 days after symptom onset. Polymerase chain reaction (PCR)–based tests may be used but vary in terms of technique and sensitivity. A skin biopsy of a lesion obtained with a 3-mm punch biopsy can help establish diagnosis and should be performed before or within 12 hours of administering antibiotics. Other findings common in advanced disease—reflecting vascular injury, permeability, and host response—may include: Hyponatremia Thrombocytopenia Elevated aminotransferases Hyperbilirubinemia Azotemia. TREATMENT Empiric therapy following a tick bite is not recommended; however, if a symptomatic patient is suspected of having RMSF, empiric treatment should not be delayed. Delayed treatment associated with increased mortality Treatment with doxycycline 100 mg orally or intravenously twice daily for 5 to 7 days, or for at least 3 days after fever subsides, is the treatment of choice. Recommended for all ages, including young children, and pregnant women Single 200-mg loading dose can be administered in critically ill patients Chloramphenicol is the only known alternative agent for treatment of RMSF but is rarely given, owing to its side effect profile, unless the patient has a severe adverse reaction to doxycycline. Supportive management includes fluids, pain relievers, and fever reducers. PREVENTION Prophylaxis with doxycycline is not recommended following tick exposure. Preventive measures include wearing protective clothing, using tick-repellent chemicals, and performing frequent tick checks to ensure prompt removal while in endemic areas. CASE CONCLUSION This patient represents a classic example of RMSF presentation. Based on the history and physical examination findings, a presumptive diagnosis of RMSF was made. The patient was prescribed a 7-day course of twice-daily oral doxycycline 100 mg and made a complete recovery. Box 2