Review Question - QID 101647

This patient's presentation is suggestive of an opportunistic fungal infection. Aspergillus fumigatus appears as septate hyphae that branch at acute angles, often in a V-shaped pattern.

Immunocompromised individuals and patients with chronic granulomatous disease such as tuberculosis are especially prone to aspergillus fumigatus infection. Invasive aspergillosis most commonly affects the lungs with symptoms of hemoptysis and granulomas but also has a predilection for blood vessels and hematogenous spread. Amphotericin B or voriconazole is indicated for treatment. Aspergillosis may also cause allergic bronchopulmonary aspergillosis in patients with asthma or cystic fibrosis, or aspergillomas (‘fungus balls’) in patients with lung cavities.

Sherif and Segal review pulmonary aspergillosis; they conclude that the diagnosis of invasive aspergillosis is challenging, often with varying levels of certainty. Either demonstration of invasive hyphae histologically or a positive culture from a normally sterile environment (e.g. pleural fluid) is typically required to prove the presence of invasive fungal disease.

Khalsa discusses the prevention of opportunistic infections in HIV-positive patients, concluding that initial preventive interventions should include: patient education to decrease exposure to infections, treatment of comorbid conditions, and vaccinations, such as those for pneumococcus and hepatitis B. Prophylaxis is generally recommended when CD4+ cell counts fall below 200.

Illustration A shows aspergillus fumigatus stained with PAS.

Incorrect Answers:
Answer 1: Mycobacterium tuberculosis may cause caseous granulomas in the lungs, but it appears microscopically as acid-fast rods.
Answer 2: Candida albicans infection typically manifests as oral and esophageal thrush in immunocompromised patients, but it may affect any organ as disseminated candidiasis. C. albicans appears microscopically in both pseudohyphae branching at right angles and budding yeast forms.
Answer 3: Pneumocystis jiroveci is a common cause of diffuse interstitial pneumonia in immunocompromised patients. Upon methenamine silver stain it appears as a disk-shaped yeast.
Answer 5: Naegleria fowleri is an amoeba that causes rapidly fatal meningoencephalitis. The organism is encountered in freshwater lakes.