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Histoplasma capsulatum is a soil saprophyte that grows well in soil enriched with bird droppings. The usual disease is self-limited, affects the lungs, and is asymptomatic. Chronic cavitary pulmonary disease, disseminated disease, and meningitis may occur and can be fatal, especially in young children and immunosuppressed patients.
Aiding in the diagnosis of Histoplasma meningitis
Any positive serologic result in spinal fluid is significant.
Simultaneous appearance of the H and M precipitin bands indicates active histoplasmosis.
The M band alone indicates active or chronic disease or a recent skin test for histoplasmosis.
Antibody levels may be low in spinal fluid in cases of Histoplasma meningitis.
Histoplasmin skin tests yield specific antibodies in titratable quantity, and may cause difficulties in interpretation.
Cross-reacting antibodies with coccidioidomycosis or blastomycosis may cause false-positive results for Histoplasmosis.
Mycelial by CF: negative (positives reported as titer)
Yeast by CF: negative (positives reported as titer)
Antibody by immunodiffusion: negative (positives reported as band present)
Kaufman L, Kovacs JA, Reiss E: Clinical immunomycology. In Manual of Clinical and Laboratory Immunology, Washington, DC, ASM Press.1997