(See also See also Fungal Skin Infections.)
Fungal infections are often classified as opportunistic or primary. Opportunistic infections are those that develop mainly in immunocompromised hosts; primary infections can develop in immunocompetent hosts. Fungal infections can be systemic or local. Local fungal infections typically involve the skin (see Fungal Skin Infections), mouth (see Symptoms of Dental and Oral Disorders: Stomatitis), and vagina (see Vaginitis, Cervicitis, and Pelvic Inflammatory Disease (PID): Candidal Vaginitis) and may occur in normal or immunocompromised hosts.
Opportunistic fungal infections
Many fungi are opportunists and are usually not pathogenic except in an immunocompromised host. Causes of immunocompromise include AIDS, azotemia, diabetes mellitus, bronchiectasis, emphysema, TB, lymphoma, leukemia, other hematologic cancers, burns, and therapy with corticosteroids, immunosuppressants, or antimetabolites. Patients who spend more than several days in an ICU can become compromised because of medical procedures, underlying disorders, and undernutrition.
Typical opportunistic systemic fungal infections (mycoses) include
Systemic mycoses affecting severely immunocompromised patients often manifest acutely with rapidly progressive pneumonia, fungemia, or manifestations of extrapulmonary dissemination.
Primary fungal infections
These infections usually result from inhalation of fungal spores, which can cause a localized pneumonia as the primary manifestation of infection. In immunocompetent patients, systemic mycoses typically have a chronic course; disseminated mycoses with pneumonia and septicemia are rare and, if lung lesions develop, usually progress slowly. Months may elapse before medical attention is sought or a diagnosis is made. Symptoms are rarely intense in such chronic mycoses, but fever, chills, night sweats, anorexia, weight loss, malaise, and depression may occur. Various organs may be infected, causing symptoms and dysfunction.
Primary fungal infections may have a characteristic geographic distribution, which is especially true for the endemic mycoses caused by certain dimorphic fungi. For example,
However, travelers can manifest disease any time after returning from endemic areas.
When fungi disseminate from a primary focus in the lung, the manifestations may be characteristic, as for the following:
If clinicians suspect an acute or a chronic primary fungal infection, they should obtain a detailed travel and residential history to determine whether patients may have been exposed to certain endemic mycoses, perhaps years previously.
Pulmonary fungal infections must be distinguished from TB, tumors, and chronic pneumonias caused by nonfungal organisms. Specimens are obtained for fungal and acid-fast bacilli culture and histopathology. Sputum samples may be adequate, but occasionally bronchoalveolar lavage, transthoracic needle biopsy, or even surgery may be required to obtain an acceptable specimen.
Fungi that cause primary systemic infections are readily recognized by their histopathologic appearance. However, identifying the specific fungus may be difficult and usually requires fungal culture. The clinical significance of positive sputum cultures may be unclear if they show commensal organisms (eg, Candida albicans) or fungi ubiquitous in the environment (eg, Aspergillus sp). Therefore, evidence of tissue invasion is required for a diagnosis of candidiasis, aspergillosis, or other opportunistic fungal infections (eg, fusariosis, pseudallescheriasis) because these fungi may not be causing the symptoms.
Serologic tests may be used to check for many systemic mycoses if culture and histopathology are unavailable or unrevealing, although few provide definitive diagnoses. Particularly useful tests include the following:
Most other tests for antifungal antibodies have low sensitivity, specificity, or both and, because measurement of acute and convalescent titers is required, cannot be used to guide initial therapy.
Last full review/revision April 2009 by Alan M. Sugar, MD