Pneumonia is the leading infectious cause of death in developed countries. Among the vast diversity of respiratory pathogens, fungi account for only a small portion of community-acquired and nosocomial pneumonias. However, fungal respiratory infections generate concern in the expanding population of immunosuppressed patients. Fungi may colonize body sites without producing disease or they may be a true pathogen, generating a broad variety of clinical syndromes.

Fungal pneumonia is an infectious process in the lungs caused by one or more endemic or opportunistic fungi. Fungal infection occurs following the inhalation of spores, after the inhalation of conidia, or by the reactivation of a latent infection. Hematogenous dissemination frequently occurs, especially in an immunocompromised host.

Endemic fungal pathogens (eg, Histoplasma capsulatum, Coccidioides immitis, Blastomyces dermatitidis, Paracoccidioides brasiliensis,Sporothrix schenckii, Cryptococcus neoformans) cause infection in healthy hosts and in immunocompromised persons, in defined geographic locations of the Americas and around the world.

Opportunistic fungal organisms (eg, Candidaspecies, Aspergillus species, Mucor species) tend to cause pneumonia in patients with congenital or acquired defects in the host immune defenses.

The diagnosis of fungal pneumonias is difficult to prove, and is often made on a presumptive basis. It relies on a combination of clinical, radiologic, and microbiological factors. Nonmolecular fungal markers in serum or other biological samples represent a noninvasive diagnostic tool, which can help in therapeutic decisions.

The individual prognosis is often linked to the severity and outcome of the underlying disease and to whether a reversal of factors affecting the patient’s immune status is possible.

Complications of fungal pneumonia includes disease dissemination to other sites (ie, brain, meninges, skin, liver, spleen, kidneys, adrenals, heart, eyes) and sepsis syndrome and  blood vessel invasion, which can lead to hemoptysis, pulmonary infarction, myocardial infarction, cerebral septic emboli, cerebral infarction, or blindness.

Other complications may include the following:

• Bronchopleural or tracheoesophageal fistulas

• Chronic pulmonary symptoms

• Mediastinal fibromatosis (histoplasmosis)

• Broncholithiasis (histoplasmosis)

• Pericarditis and other rheumatologic symptoms

Treatment of fungal infection

Therapy for fungal pneumonias must include antifungal agents. The type of antifungal drug employed must be selected based on the particular pathogen that is isolated or that is clinically suspected. Many classes of antifungal agents are now available, including the classic antibiotics; first-, second-, and third-generation triazoles; and the echinocandins. Amphotericin B is less frequently used and, when used, is often given as a liposomal formulation to decrease toxicity.