A 25-year-old complains of fever, nausea, and myalgias for 5 days, and now has developed a macular rash over his wrists, palms, ankles, and soles with some petechial lesions. The rash recently ascended to his arms and legs. The patient recently returned from a summer camping trip in Tennessee.
Which of the following is the most likely cause of the rash?
A. Contact dermatitisThe rash described is most consistent with Rocky Mountain spotted fever, for which a tick is the intermediate vector. Secondary syphilis could present with a macular rash in the same distribution, but does not cause an acute febrile syndrome with myalgia. Always think of these two diagnoses when a rash begins on the palms and soles. Contact dermatitis does not cause petechial lesions. The skin lesions in disseminated gonococcal infection can be distal, but are usually few in number and are pustular. Giardiasis is acquired from contaminated water but does not cause fever or a rash. Trichinosis, acquired from the ingestion of contaminated pork, can cause myalgias and a maculopapular rash, but rarely shows the distal involvement seen in this patient. Trichinosis causes prominent periorbital edema and eosinophilia.