A 49-year-old man comes to the office due to 4 months of cough and weight loss. His medical history is otherwise unremarkable and he takes no medications. The patient is a farmer who lives in Mississippi. He does not use tobacco, alcohol, or illicit drugs. His temperature is 37.9 C (100.2 F). Examination shows right lobe crackles. Chest x-ray reveals a pulmonary infiltrate in the right upper lobe. Bronchoscopy with transbronchial biopsy shows granulomatous inflammation. HIV testing is negative. Which of the following is most likely causing this patient's symptoms?

Question

A 49-year-old man comes to the office due to 4 months of cough and weight loss.  His medical history is otherwise unremarkable and he takes no medications.  The patient is a farmer who lives in Mississippi.  He does not use tobacco, alcohol, or illicit drugs.  His temperature is 37.9 C (100.2 F).  Examination shows right lobe crackles.  Chest x-ray reveals a pulmonary infiltrate in the right upper lobe.  Bronchoscopy with transbronchial biopsy shows granulomatous inflammation.  HIV testing is negative.  Which of the following is most likely causing this patient's symptoms?

Quizplus · Accepted Answer

Blastomyces dermatitidis is a dimorphic fungus that can cause pulmonary infections in immunocompetent people and should be considered in individuals from an endemic area (states adjacent to and east of the Mississippi and Ohio river valleys; some overlap with Histoplasmosis). The fungus exists in the environment in mold form and is found in soil, organic matter, and many animals (eg, dogs, horses). It is transmitted by the respiratory route, entering the lungs and transforming into yeast form (thermal dimorphism). B dermatitidis infection can be asymptomatic or it can mimic community-acquired pneumonia (resolves spontaneously) or chronic pneumonia (may be indistinguishable from tuberculosis, other fungal infections, or cancer). Pulmonary blastomycosis is characterized by granuloma formation. Extrapulmonary disease (skin, bone, and genitourinary system) occurs in immunocompromised patients. Examination of tissues or respiratory fluids shows round yeast with thick walls and broad-based budding. Itraconazole is the preferred treatment for blastomycosis. (Choice B) Candida albicans is an opportunistic pathogen. It may cause superficial infections (eg, vulvovaginitis) in an immunocompetent host. Systemic disease, however, occurs only in the immunosuppressed (especially neutropenic patients). (Choice C) Mucor species infect the paranasal sinuses in patients with neutropenia, burns, or diabetes mellitus. Mucormycosis is strongly associated with diabetic ketoacidosis. (Choice D) Penicillium marneffei is an opportunistic infection in immunocompromised patients, primarily those with AIDS, in Southeast Asia. It is rare in immunocompetent individuals. (Choice E) Pneumocystis jiroveci causes pulmonary disease in immunocompromised patients, particularly those with HIV. P jiroveci does not cause symptoms in immunocompetent hosts. Educational objective: Blastomyces dermatitides can cause pulmonary disease in the immunocompetent host. Dissemination (most commonly to skin and bones) occurs in immunocompromised individuals.

A 49-Year-Old Man Comes to the Office Due to 4