Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (486 page)

   Patients with invasive sinusitis due to
Aspergillus
usually present with fever, epistaxis, nasal congestion, facial edema, and pain over the affected sinuses. Infection may extend to the cavernous sinus, orbit (blurred vision, proptosis, chemosis), or CNS (mental status changes and a variety of specific symptoms related to the affected area). Endocarditis, endophthalmitis, skin infection, and GI infection are well-described infections associated with invasive aspergillosis, presumably due to hematologic dissemination from a primary site of infection.

   
Aspergillus
species may cause noninvasive diseases in immunocompetent patients. Allergic bronchopulmonary aspergillosis (APBA) occurs in 1–2% of patients with chronic asthma. Patients present with exacerbation of asthma symptoms, including increased and recurrent bronchial obstruction. Fever and malaise are common. Brownish mucous plugs or blood may be seen in expectorated sputum. APBA may respond to glucocorticoid therapy. Diagnosis is usually based on a number of major criteria, including history of asthma, immediate skin test reactivity to
Aspergillus
antigens, precipitin antibodies to
Aspergillus
species, total serum IgE >1,000 ng/mL, peripheral blood eosinophilia >500/mm
³
, radiographic abnormalities, and elevation of serum anti-
Aspergillus
IgE and IgG.

   Fungus balls may form by colonization and proliferation of
Aspergillus
species in lung cavities formed by unrelated disease. Disease may result from erosion into critical structures.

   Laboratory Findings

Culture
: Blood cultures are rarely positive, even in patients with evidence of hematogenous spread.

Histopathology
: The morphology of
Aspergillus
is fairly characteristic, usually demonstrating nonpigmented, narrow, septate hyphae with acute angle branching. Angioinvasion is commonly demonstrated. The morphology, however, is not specific; other molds, like
Scedosporium
or
Fusarium
, may show a similar histopathology.

Core laboratory
: Laboratory studies related to the function of affected organs should be submitted. Eosinophilia (>1,000/μL; often >3,000/μL) is common in ABPA.

BLASTOMYCOSIS

   Definition

Blastomycosis is caused by the thermally dimorphic fungus
Blastomyces dermatitidis
. Most cases are reported from the North America; endemic areas include southeastern, south central and midwestern states (especially around the Mississippi and Ohio River basins), north central states and Canadian provinces bordering the Great Lakes, and St. Lawrence River basin. Blastomycosis is also endemic in regions of Africa and may occur sporadically in patients in other areas.

   Who Should Be Suspected?

   The scope of pulmonary infection ranges from asymptomatic or mild infection to acute or chronic pulmonary infection to disseminated extrapulmonary disease. Immunocompromised patients are more susceptible to severe, extrapulmonary, and recurrent disease. Infection may spread to secondary sites.

   Conditions associated with increased risk include AIDS, cytotoxic and immunosuppressive therapy, hematologic malignancy, pregnancy, and solid organ transplantation.

   Laboratory Findings

   Direct detection: Wet mount or calcofluor white preparation has moderate sensitivity for early diagnosis of blastomycosis. Sensitivity is improved by the use concentrated specimens.

   Histopathology: Frequently demonstrates pyogranulomas in infected tissues. Visualization of characteristic yeast forms is improved by the use of fungal stains, like periodic acid–Schiff or methenamine silver stains.