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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.
The dimorphic fungus, Blastomyces dermatitidis, causes blastomycosis. When the organism is inhaled, it causes pulmonary disease-cough, pain, and hemoptysis, along with fever and night sweats. It commonly spreads to the skin, bone, or internal genitalia where suppuration and granulomas are typical. Occasionally, primary cutaneous lesions after trauma are encountered; however, this type of infection is uncommon. Central nervous system disease is uncommon.
Aiding in the diagnosis of Histoplasma meningitis
Detection of antibodies in patients having blastomycosis
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.
A positive result indicates that IgG and/or IgM antibodies to Blastomyces were detected. The presence of antibodies is presumptive evidence that the patient was or is currently infected with (or exposed to) Blastomyces.
A negative result indicates that antibodies to Blastomyces were not detected, but does not rule out infection.
All specimens testing equivocal will be repeated. Specimens testing equivocal after repeat testing should be submitted for further testing by another conventional serologic test (eg, CBL / Blastomyces Antibody by Immunodiffusion, Spinal Fluid).
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.
A negative result does not rule out blastomycosis.
Cross-reactivity may occur with other fungal infections such as Aspergillus, Coccidioides, or Histoplasma.
HISTOPLASMA ANTIBODY, SPINAL FLUID
Mycelial by complement fixation: Negative
Yeast by complement fixation: Negative
Antibody by immunodiffusion: Negative
BLASTOMYCES ANTIBODY BY EIA, SPINAL FLUID
1. Kaufman L, Kovacs JA, Reiss E: Clinical immunomycology. In Manual of Clinical Laboratory Immunology. Fifth edition. Edited by NR Rose, EC De Macario, JD Folds, et al. Washington DC, ASM Press, 1997
2. Kaufman L, Kovacs JA, Reiss E: Clinical immunomycology. In Manual of Clinical Laboratory Immunology. Fifth edition. Edited by NR Rose, EC De Macario, JD Folds, et al. Washington DC, ASM Press, 1997, pp 588-589