Case Study

Case Study

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Match the most likely micro-organism with the clinical scenario:

A 35-year-old woman, recently returned from a hiking trip in Arizona, presents with low-grade fever, cough with minimum clear sputum production, and rash. She is otherwise healthy with no significant past medical history. She has been on treatment with albuterol for intermittent asthma and she does have seasonal allergies.

A) Coccidioides immitis
B) Measles virus (rubeola)
C) Mycobacterium tuberculosis
D) Mycoplasma pneumoniae
E) Histoplasmosis

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Answer and Explanation 

The correct answer is Choice A.

The main clues in this question are a) the geographical location and b) the presence of a rash.

In Arizona, coccidioidal pneumonia (also called Valley Fever) accounts for around 18-29% of CAP cases. Getting a true estimate of the frequency is difficult because:

-the case numbers in the studies to date have been small
-paired sera are required and compliance can be poor
-the sensitivity of serological testing is below 100%
-many clinicians do not test for coccidioidal infection unless -patients have failed to respond to conventional therapy
-coccidioidal infection is often self-limiting, and so many antibiotic "successes" are really just the disease burning out
-in many cases symptoms are extremely mild

The incidence appears to be rising (now 75-85 cases per 100,000 population per year), and is highest in Arizona (60% of USA symptomatic cases) and California. New tests such as urinary antigen detection are coming on-line. Symptoms vary from mild common cold symptoms to cough, fever and shortness of breath, typical of CAP. The presence of a rash is significantly more frequent than with most of the common bacterial causes of CAP.

Coccidioides immitis is a dimorphic fungus, and azoles (itraconazole > posaconazole > voriconazole) are the standard treatment, although lipid preparations of amphotericin B are also effective. There is some data to suggest that patients treated with antifungals are at higher risk of relapse after therapy stops, although these patients will generally have been more ill at the start.

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