infectious diseases
Histoplasmosis
Introduction
Histoplasmosis is a pulmonary and hematogenous disease caused byHistoplasma capsulatum; it is often chronic and usually follows an asymptomatic primary infection. Symptoms are those of pneumonia or of nonspecific chronic illness. Diagnosis is by identification of the organism in sputum or tissue or use of specific serum and urine antigen tests. Treatment, when necessary, is withamphotericin Bor an azole. (See also Overview of Fungal Infections .) Histoplasmosis occurs worldwide, including parts of Central and South America, Africa, Asia, and Australia. In the United States, the endemic area for histoplasmosis includes The Ohio–Mississippi River valleys extending into parts of northern Maryland, southern Pennsylvania, central New York, and Texas Bat cave–associated outbreaks have occurred worldwide and in the United States have been reported in Florida, Texas, and Puerto Rico. H. capsulatumis a dimorphic fungi that grows as a mold in nature or in culture at room temperature but converts to a small (1 to 5 micrometers in diameter) yeast cell at 37°C and during invasion of host cells. Infection follows inhalation of conidia (spores produced by the mycelial form of the fungus) in soil or dust contaminated with bird or bat droppings. Risk of infection is greatest when tree or building removal generates airborne spores (eg, at construction sites in areas habituated by birds or bats) or when exploring caves. Risk factorsfor severe histoplasmosis include Heavy, prolonged exposure Age ≥ 55 years Infancy Compromised T-cell–mediated immunity (eg, in those who have HIV/AIDS or an organ transplant or who are taking immunosuppressants such as corticosteroids or tumor necrosis factor inhibitors) Initial infection occurs in the lungs and usually remains there but may spread hematogenously to other organs if it is not controlled by normal cell-mediated host defenses. Progressive disseminated histoplasmosis is one of the defining opportunistic infections for Human Immunodeficiency Virus (HIV) Infection . 