An 18-year-old Iowan dirt bike racer, who raced for the first time in the desert southwest 3 weeks ago, presents in September with cough, malaise, low-grade fever, myalgias, and chest pain. Rales are heard and respiratory infiltrates are noted on radiograph. Sputum stained with calcofluor white and viewed on an ultraviolet microscope shows large blue-white fluorescing spherical structures (with a wall) and with numerous small round cells inside. What is the most likely causative agent?

Question

Quizplus · Accepted Answer

The causative agent can only be Coccidioides immitis from the description of the spherules and endospores in the sputum. Note that no definitive geographic clue is given in this question. Without the results of the microscopic examination it possibly could have been Histoplasma capsulatum or Blastomyces pneumonia. The patient is also the right age group for Mycoplasma pneumonia, but again the microscopic data point instead to Coccidioides.

An 18-Year-Old Iowan Dirt Bike Racer, Who Raced for the First