Internal Medicine

0521779407-18 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:20

Rocky Mountain Spotted Fever 1309

■Physical Signs: Nonpruritic rash (macular, maculopapular or

petechial) beginning 3–5 days after onset of fever, usually around

wrists and ankles or trunk. Rash present in 49% at day 3 and 80%

day 6. Palm and sole distribution late and uncommon.

■Generalized lymphadenopathy, hepatosplenomegaly

■Neurologic defects (ataxia, seizures, coma, focal defects)

■Arrhythmias, peripheral edema

■Conjunctivitis

■May have evidence of tick bites

tests

Laboratory

■Basic Blood Tests

➣Hyponatremia more pronounced than with Colorado tick fever,

ehrlichiosis, typhus, tularemia or dengue fever

➣Elevated BUN and Cr

➣Mildly elevated LFTs, especially ALT, alkaline phosphatase

➣Anemia and low platelets

➣Normal WBC with left shift

➣Prolonged PT, PTT

Specific Diagnostic Tests

■Blood cultures to rule out other bacterial etiologies

■Serology: Indirect immunofluorescence is usually negative at pre-

sentation, >1:64 by 7–10 days after onset. 94–100% sensitive; 100%

specificity.

■Skin biopsy of rash with direct immunofluorescence and immuno-

peroxidase test: 70% sensitive, 100% specific.

differential diagnosis

■Measles, rubella, typhoid fever, murine typhus, upper respiratory

infection, gastroenteritis, enteroviral infection, disseminated gonor-

rhea, secondary syphilis, rickettsial pox, ehrlichiosis, Lyme disease,

leptospirosis, meningococcemia, boutonneuse fever, dengue fever,

Colorado tick fever, tularemia, infectious mononucleosis, acute HIV

infection, immune complex vasculitis, idiopathic thrombocytopenic

purpura, thrombotic, thrombocytopenic purpura, drug reaction

management

What to Do First

■Must maintain high diagnostic suspicion and treat based on clinical

diagnosis