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Fungal pneumonia is an infectious process in the lung caused by any one or a combination of endemic or opportunistic fungi. Endemic fungal pathogens (eg, Histoplasma capsulatum, Coccidioides immitis, Blastomyces dermatitidis, Paracoccidioides brasiliensis) cause infection in both healthy and immunocompromised hosts in defined geographic locations of the Americas and around the world. Opportunistic fungal organisms (eg, Candida species, Aspergillus species, Mucor species, Cryptococcus neoformans) tend to cause pneumonia in patients with congenital or acquired defects in their host defenses.
Fungal pneumonia is an infection of the lungs by fungi. It can be caused by either endemic or opportunistic fungi or a combination of both.
Specific instances of fungal infections that can manifest with pulmonary involvement include:
- histoplasmosis, which has primary pulmonary lesions and hematogenous dissemination
- coccidioidomycosis, which begins with an often self-limited respiratory infection (also called "Valley fever" or "San Joaquin fever")
- pulmonary blastomycosis
- sporotrichosis - primarily a lymphocutaneous disease, but can involve the lungs as well
- cryptococcosis - contracted through inhalation of soil contaminated with the yeast, it can manifest as a pulmonary infection and as a disseminated one
- aspergillosis, resulting in invasive pulmonary aspergillosis
- rarely, candidiasis has pulmonary manifestations in immunocompromised patients.
Fungal pneumonias are rare but important. Sometimes the clinical presentation is identical to more common bacterial or atypical pneumonias. In such cases, the diagnosis is either not made or is made accidentally from diagnostic specimens obtained to determine the likely bacterial pathogen. Other cases look like routine bacterial or atypical pneumonia at presentation but do not improve or even progress as they are being treated with appropriate antibacterial agents. In such cases, it is important not to give a series of treatment courses with different antibacterial antibiotics that all cover essentially the same range of pathogens. Rather the diagnostic efforts must be escalated, progressing to more aggressive measures (fiberoptic bronchoscopy, fine needle aspiration, and rarely thoracoscopic or traditional open lung biopsy) until a specific diagnosis is reached. In some cases, there are clinical clues that point to a fungal cause. Attention to these clues can lead to early initiation of appropriate diagnostic sequences, faster diagnosis, and earlier initiation of specific therapy.
Fungi typically enter the lung with inhalation of their spores, though they can reach the lung through the bloodstream if other parts of the body are infected. Also, fungal pneumonia can be caused by reactivation of a latent infection. Once inside the alveoli, fungi travel into the spaces between the cells and also between adjacent alveoli through connecting pores. This invasion triggers the immune system to respond by sending white blood cells responsible for attacking microorganisms (neutrophils) to the lungs. The neutrophils engulf and kill the offending organisms but also release cytokines which result in a general activation of the immune system. This results in the fever, chills, and fatigue common in bacterial and fungal pneumonia. The neutrophils and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation.
Fungal Pneumonia Causes
Fungal Pneumonia Symptoms
Fungal Pneumonia Diagnosis and Treatment
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