Review Question - QID 217672

Cryptococcus neoformans can cause opportunistic infections in patients with human immunodeficiency virus (HIV) infection, is often found in pigeon droppings, has a thick capsule on India ink staining, and has a polysaccharide capsular antigen that is detected on latex agglutination testing. Pulmonary cryptococcosis is the most common clinical manifestation of symptomatic infection with C. neoformans.

C. neoformans is a non-dimorphic fungus that is found in soil and pigeon droppings that can cause infection via inhalation. Following inhalation, C. neoformans can deposit in the alveoli and terminal bronchioles, leading to focal pneumonitis. In some patients, especially those who are immunocompromised, C. neoformans can then disseminate and cause disease in the central nervous system, soft tissues, skin, and/or bones. Diagnosis can be made with visualization of encapsulated yeast on bronchoalveolar lavage, fungal culture, detection of serum cryptococcal antigen, and a few well-defined noncalcified pleural-based nodules on chest radiography. Lumbar puncture is only needed in patients with neurologic symptoms, very high serum cryptococcal antigen titer, or an underlying immunocompromised state. Treatment of symptomatic, uncomplicated pulmonary cryptococcosis is generally with fluconazole.

Srikanta et al. review the discovery, microbiology, epidemiology, and clinical presentation of Cryptococcus neoformans infection.

Figure/Illustration A shows a photomicrograph of Cryptococcus neoformans using an India ink staining preparation. The characteristic thick capsule is indicated by the concentric blue circles and red arrow.

Incorrect Answers:
Answer 1: Bone can be affected in fewer than 10% of cases of disseminated cryptococcosis. The vertebrae are the most common site of osteoarticular infection and radiography generally shows well-circumscribed osteolytic lesions.

Answer 2: The brain, meninges, and central nervous system (CNS) are often affected in disseminated C. neoformans infection. Infection is typically indolent, with fever, malaise, headache, neck stiffness, photophobia, and vomiting developing over 1 to 2 weeks. However, cryptococcal meningoencephalitis is less common than pulmonary infection. Treatment of complicated cryptococcosis, including cryptococcal meningoencephalitis, is with amphotericin B, flucytosine, and fluconazole.

Answer 3: The colon can occasionally be affected in disseminated cryptococcosis. By contrast, cryptosporidium are a genus of protozoa that can cause gastroenteritis in both immunodeficient and immunocompetent patients.

Answer 5: Skin can be affected in up to 15% of patients with disseminated cryptococcosis. It can manifest as papules, plaques, ulcers, cellulitis abscesses, sinus tracts, or umbilicated lesions resembling molluscum contagiosum.

Bullet Summary:
The lungs are the most common site of infection with Cryptococcus neoformans.