Histoplasmosis
GENERAL PRINCIPLES
• Histoplasma capsulatum var. capsulatum is a dimorphic fungus (yeast in tissues; mold in the environment) that grows in soil contaminated by bat or bird droppings.35
• Histoplasmosis is the most common endemic mycosis diagnosed in the US.
The highest areas of endemicity are along the Ohio and Mississippi River Valleys. Histoplasmosis is also common throughout Latin America.DIAGNOSIS
• Clinical manifestations are extremely varied, including acute flu-like symptoms, chronic granulomatous pulmonary disease, or fulminant multiorgan failure in immunocompromised patients.
• Diagnosis is based on culture or histopathology, antigen assay (urine, blood, or CSF), or antibody detection assays using a complement fixation (CF) test, with titers of 1:8 seen in most patients and titers >1:32 highly suggestive of active infection. The urine antigen assay is the most sensitive test for detecting acute and disseminated disease and is helpful in following response to therapy. Antibody assays are useful in subacute and chronic disease; antigen assays are less sensitive.
TREATMENT
See Table 14-13.