Fungus Infections

Fungus Infections, diseases caused by the growth of fungi in or on the body. In most healthy people fungal infections are mild, involving only the skin, hair, nails, or other superficial sites, and they clear up spontaneously. They include the familiar ringworm and athlete's foot. In someone with an impaired immune system, however, such infections, called dermatophytoses, can persist for long periods. The organisms causing dermatophytoses belong to the genera Microsporum, Epidermophyton, and Trichophyton.

Fungi can also invade internal organs of the body, especially the lungs, where the infections resemble pneumonia or pulmonary tuberculosis. These infections usually occur in people whose immune system has been suppressed by diseases such as acquired immunodeficiency syndrome (AIDS), by anticancer drugs, or by radiation; patients being treated with steroid hormones (see Hydrocortisone); people with diabetes; and those being treated with antibiotic drugs for a long time. Two fungi often found in such cases are Cryptococcus and Aspergillus, which are called opportunistic pathogens.

Systemic infections also occur in healthy people, involving the fungi Blastomyces;Histoplasma, endemic to the midwestern United States; or Coccidioides, endemic to the southwestern United States. The infectious agents Nocardia and Actinomyces, formerly classed as fungi, are now considered bacteria.

Fungi belonging to the genus Candida, especially Candida albicans, can infect both internal organs and mucous membranes of the mouth (see Thrush), throat, and genital tract. In people with impaired immunity, this organism can cause a chronic infection.

Many drugs are available for treating fungal infections. These include both intravenous and oral drugs, and many agents are available for topical (local) application. Persons chronically infected with Candida,Histoplasma, or Cryptococcus may require long-term therapy with an oral or an intravenous drug.