Tick Time: An Early Summer Quiz for Rheumatologists

May 21, 2014

Tick season is here again, along with rashes and arthralgias. Here's a quick quiz to remind you of tick-borne disorders and their mimics.

Once again, for anyone who treats achy limbs, it's the season to be alert for the presence of ticks, the absence of ticks, and the mimics of tick-borne disorders. Here, to refresh your memory, a few quick quizzes.


[[{"type":"media","view_mode":"media_crop","fid":"24644","attributes":{"alt":"Rocky Mountain spotted fever","class":"media-image media-image-right","height":"135","id":"media_crop_8182667661887","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"2145","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"float: right;","title":" ","typeof":"foaf:Image","width":"242"}}]]1.  A 55-year-old truck driver who lives in the rural Midwest is hospitalized with fever, headache, poor appetite, a blanching rash, and diffuse pain. His illness began 6 days earlier with fever and aching in his joints. He then noticed small red spots on his forearms and legs that later spread to his trunk, palms, and soles.

He suspects he was exposed to poison ivy in the woods behind his home, where he keeps 10 dogs. His wife found a brown tick in his umbilicus a week earlier.

Which of the following conditions in the differential diagnosis do you suspect?

A. Allergic contact dermatitis

B. Ehrlichiosis

C. Rocky Mountain spotted fever

D. Lyme disease

E. Murine typhus

F. Scrub typhus

G. Secondary syphilis

H. Erythema multiforme

Correct answer

Discussion

C. Rocky Mountain spotted fever. The history of a tick bite followed by fever, myalgia, arthralgia, and a diffuse rash on palms and soles that spreads from the extrem-ities to the torso strongly suggests Rocky Mountain spotted fever. For further discussion, see Rash and Fever: Is the Cause Benign or Potentially Dangerous?

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2.  [[{"type":"media","view_mode":"media_crop","fid":"24645","attributes":{"alt":"myopathy","class":"media-image media-image-right","height":"139","id":"media_crop_1441841209590","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"2146","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"float: right;","title":" ","typeof":"foaf:Image","width":"150"}}]]A 55-year-old man presents with complaints of myalgias of approximately 1 week’s duration. You note mild muscle tenderness.

He has recently overcome an episode of sinusitis, treated at a walk-in clinic with decongestants, nasal corticosteroids, and 500 mg clarithromycin bid. 

One month before this visit, the patient and his wife had been camping in North Carolina. While he denied any insect bites during his trip, many individuals who have been bitten are unaware of their exposure.

Vital signs are normal, and you note no jaundice, rashes, lymphadenopathy, or synovitis. Findings from heart, lung, and abdominal examinations are normal. He is taking 25 mg/day of hydrochlorothiazide for hypertension and 40 mg/day of simvastatin for hyperlipidemia.

Which of the following tests would you order?

A. Lyme titer

B. Rickettsia titer

C. Creatine phosphokinase level

D. Erythrocyte sedimentation rate

E. Muscle biopsy

Correct answer.

Discussion

C. Creatinine phosphokinase level. The rationale behind this option is to identify a potential drug-drug interaction-in this case between simvastatin and clarithromycin. For further discussion, see Myalgias in a 55-Year-Old Man, After a Camping Trip.

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3.   Recent research has clarified the signs that differentiate septic arthritis from Lyme arthritis. Among the following, which is the best indication that a patient has septic arthritis rather than Lyme arthritis?

A.  Fever

B.  High synovial fluid cell count

C.  Refusal to bear weight on the affected limb.

Correct answer

DiscussionC. Refusal to bear weight on the affected limb. However, a patient with septic arthritis was 4.43 times more likely than one with Lyme arthritis to have a fever and 3.63 times more likely to have a high synovial fluid cell count.

For further information, see Differentiating Lyme Arthritis from Septic Arthritis: Clues Uncovered.

The same research team subsequently published in Pediatrics a clinical prediction model of laboratory values that can help avoid unnecessary arthrocentesis. See Distinguishing Lyme From Septic Knee Monoarthritis in Lyme Disease–Endemic Areas.

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4.  This is an image of the Lone Star tick Amblyomma americanum (Lone Star tick), which is associated with southern tick–associated rash illness (STARI), also called Lyme-like illness, southern Lyme disease, or Masters disease. Which of the following characterize STARI?

[[{"type":"media","view_mode":"media_crop","fid":"24632","attributes":{"alt":"STARI Lone Star tick","class":"media-image media-image-right","height":"163","id":"media_crop_9293969173380","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"2144","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"float: right;","title":" ","typeof":"foaf:Image","width":"158"}}]]A.   Target-like rash that develops around the site of a tick bite
B.    Fever, headache, fatigue, and muscle and joint pains
C.   Serious later complications including arthritis, carditis, and neurological symptoms
D.   On hematoxylin-eosin staining, a principally lymphocytic infiltrate with numerous plasma cells
E.    A and B, but not C or D.
F.    A and D, but not B or C.
G.   All of the above

Correct answer

Discussion

E.  A and B, but not C or D. Upon presentation, STARI somewhat resembles Lyme disease, although symptoms may be milder. It is not associated with the serious late sequelae that sometimes arise after Lyme tick exposure, and on hematoxylin-eosin staining it shows a principally lymphocytic inflitrate without the plasma cells that appear with Lyme disease.