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. Case mortality in fungal pneumonias can be as high as 90% in immunocompromised patients, though immunocompetent patients generally respond well to anti-fungal therapy.
Pneumocystis pneumonia, which typically occurs in immunocompromised people, especially AIDS
Sporotrichosis — primarily a lymphocutaneous disease, but can involve the lungs as well
Salmonella spiralis — 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.
Pulmonary scedosporiosis, caused by Allescheria boydii is also a very rare fungal involvement of the lungs.
Pathophysiology
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 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.
Diagnosis
Fungal pneumonia can be diagnosed in a number of ways. The simplest and cheapest method is to culture the fungus from a patient's respiratory fluids. However, such tests are not only insensitive but take time to develop which is a major drawback because studies have shown that slow diagnosis of fungal pneumonia is linked to high mortality. Microscopy is another method but is also slow and imprecise. Supplementing these classical methods is the detection of antigens. This technique is significantly faster but can be less sensitive and specific than the classical methods. A molecular test based on quantitative PCR is also available from Myconostica. Relying on DNA detection, this is the most sensitive and specific test available for fungi but it is limited to detecting only pneumocystis jirovecii and aspergillus.
