Board Review: Bugs and Drugs


21-year-old-man who presents to the emergency department with a rash and a fever of 101.2. Patient noted a macular rash on his ankles and wrists and now has spread to the chest and back and appears petechial. Patient admits to hiking recently in North Carolina. Patient is found to have hyponatremia to 122, platelets are found to be low at 50K, and mildly elevated LFTs. Which of the following is the most likely diagnosis? 


A. Babesiosis

B. Ehrlichiosis

C. Lyme Disease

D. Rocky Moutain Spotted Fever



















Answer D: RMSF is a tick borne illness caused by Rickettsia rickettsi and most commonly occurs in the southeastern United States. Classic symptoms are fever, headache, myalgias, nausea, and vomiting. The rash is small red macules that begins on the ankles and feet and then spreads to palms and sole and thereafter centrally. In later stages, rash can become petechial.



Regional Tick Borne Illness






Geographic location

Clinical Presentation

Lab Abnormalities




SE and south central US

fever, HA, malaise, n/v/d, arthralgias. Severe: encephalitis, renal failure, respiratory distress

pancytopenia, elevated AST, hyponatremia

DNA PCR testing: Peripheral Smear->morulae in monocyte

Doxycycline 100 mg 10 days: or 3-5 days after defervescence (whichever is longer)

Human Granulocytic Anaplasmosis

NE and North Central and eastern US

1-2 wks later w/ F, HA, myalgia: Rash is RARE

transaminitis, leukopenia, thrombocytopenia

PCR, serology; Peripheral smear->morulae in granulocyte

Doxy 100 bid 10-14days


NE and North Central US

Malaise, fatigue, anorexia, shaking chills, fever, headache, nausea, vomiting, myalgias, arthralgias, dark urine, SOB

Hemolytic anemia, thrombocytopenia, transaminitis, Increased BUN and Cr

PCR, blood smear (maltese cross in RBC)

Mild to moderate: Atovaquone + azithro or clindamycin + quinine. Severe IV clinda + quinine +/- exchange transfusion

Lyme Disease

Atlantic Central and North Central US

1st stage: Erythema migrans w/ nonspecifc sx 2nd stage: fever, neuropathies (CN VII palsy), heart block, asymmetric arthritis. Late:  chronic arthritis, myocarditis, encephalopathy, polyneuropathy


ELISA or IFA (indirect Immunofluorescence)

PPX: Doxy 200 mg PO X 1 w/in 72 hrs of bite Doxycycline, amoxicillin, or cefuroxime for 14-21 days

RMSF (rocky moutain spotted fever)

Continental US, mostly south central and SE

fever, headache, rash (macules later becoming petechial) begins at ankles and wrists and spreads centrally

hyponatremia, thrombocytopenia, transaminitis

 IFA (indirect Immunofluorescence)

Doxycycline 100 mg bid for 5-7 days  or for at least 3 days after fever subsides


Wilson, K et al.  “ Whats Eating You? Ixodes Tick and Related Diseases: Part 2: Diagnosis and treatment of Regional Tick – borne Diseases.” Cutis. 2018 April ; 101(4):266-268; 305 <>

Bellis, J et al. “Tick-Borne Illness: Identification and Management in the Emergency Department.” < Sept 2, 2018.

Hu, L et al. “ Clinical Manifestations of Lymes Diseae.” May 2 2018. <> 9/26/19. 

Hu, L et al. “ Treatment of Lyme Disease.” Sept 27, 2018. <>. 9/26/19. 

Sexton, D et al. “ Clinical Manifestation and Diagnosis of Rocky Mountain spotted fever.” May 29 2018. <> .9/26/19.