Fungal Pneumonia
Three types of fungi commonly cause pneumonia: Histoplasma capsulatum, which causes histoplasmosis, Coccidioides immitis, which causes coccidioidomycosis, and Blastomyces dermatitidis, which causes blastomycosis. Most people who become infected have only minor symptoms and do not know that they are infected. Some people become gravely ill. Infections caused by other fungi occur primarily in people with a severely weakened immune system.
Histoplasmosis: Histoplasmosis occurs worldwide but is prevalent in river valleys in temperate and tropical climates. In the United States, the fungus occurs most commonly in the Mississippi and Ohio river valleys and in the river valleys of the East. More than 80% of people living in the Mississippi and Ohio river valleys have been exposed to the fungus.
After being inhaled, the fungus causes no symptoms in many people. In fact, many people learn that they have been exposed only after having a skin test or a chest x-ray that shows a nodule or enlarged lymph nodes. Calcium deposits can often be seen in these areas also. Other people may have a cough, fever, muscle aches, and chest pain. The infection may cause acute pneumonia, or it may develop into chronic pneumonia with symptoms that persist for months. Rarely, the infection spreads to other areas of the body, especially the bone marrow, liver, spleen, and digestive tract. This disseminated form of the disease tends to occur in people who have AIDS or other immune system disorders (see Section 17, Chapter 197).
Usually, the diagnosis is made by identifying the fungus in a sputum sample, by performing a blood or urine test that detects the organism, or by performing a blood test that identifies certain antibodies. Treatment typically consists of taking an antifungal drug, such as itraconazole or amphotericin B.
Coccidioidomycosis: Coccidioidomycosis (also called valley fever) occurs primarily in semiarid climates, especially the southwestern United States and certain parts of South America and Central America. After being inhaled, the fungus may cause no symptoms, or it may cause either acute or chronic pneumonia. In some cases, the infection spreads beyond the respiratory system--typically to the skin, bones, joints, and tissues covering the brain (meninges). This complication is more common in men, especially Filipinos and blacks, and in people who have AIDS or other immune system disorders (see Section 17, Chapter 197).
The diagnosis is made by identifying the fungus in a sputum sample or a sample taken from another infected area or by performing a blood test that identifies certain antibodies. Treatment typically consists of giving an antifungal drug, such as fluconazole or amphotericin B.
Blastomycosis: Blastomycosis occurs primarily in the southeastern, south central, and midwestern United States and in areas around the Great Lakes. After being inhaled, the fungus causes infection primarily in the lungs; however, the infection usually produces no symptoms. Some people have a flu-like illness. Occasionally, symptoms of a chronic lung infection last for months. The disease may spread to other parts of the body, especially the skin, bones, joints, and prostate gland (see Section 17, Chapter 197).
Usually, the diagnosis is made by identifying the fungus in sputum or in another specimen. There is no blood test for this fungus. Treatment typically consists of an antifungal drug, such as itraconazole or amphotericin B. However, many people do not require treatment.
Other Fungal Infections: These infections include cryptococcosis, caused by Cryptococcus neoformans; aspergillosis, caused by Aspergillus; and mucormycosis, caused by fungi of the order Mucorales. All these infections occur throughout the world. Cryptococcosis, the most common one, may occur in an otherwise healthy person but usually is severe only in people with underlying immune system disorders, such as AIDS (see Section 17, Chapter 197). Cryptococcosis may spread, especially to the meninges, where the resulting disease is called cryptococcal meningitis. Aspergillosis is a common and important cause of pulmonary infections in people who have acute leukemia or AIDS, have undergone organ transplantation, or are receiving long-term treatment with corticosteroids (see Section 17, Chapter 197). Mucormycosis, a relatively rare fungal infection (see Section 17, Chapter 197), occurs most often in people who have severe diabetes or leukemia. The three infections are treated with antifungal drugs, such as itraconazole, fluconazole, and amphotericin B. However, people who have AIDS or other immune system disorders may not recover from these infections.
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