Pathophysiology
1) infection with Aspergillus fumigatus (most common and serious), A. flavus, or A. niger 2) normally colonizes skin, mucous membranes, and respiratory tract, but can also cause fatal systemic illness (usually in immunosuppressed patients) 3) sinus infection occurs in three forms – fungus ball in a chronically infected sinus cavity (usually maxillary), invasive fibrous granulomatous inflammation, and allergic sinusitis 4) in lung – infection occurs in two forms – fungal ball forming in preexisting cavity and allergic bronchopulmonary aspergillosis (ABPA) 5) in eye – posterior uveitis and keratitis 6) in brain – meningitis and abscesses 7) in skin – nodular eruptions with necrosis in immunosuppressed patients
Signs and Symptoms
1) pleuritic chest pain 2) fever 3) cough 4) hemoptysis (ominous sign) 5) dark colored mucosa in nose or hard palate 6) positive wheal and flare reaction (in ABPA) 7) asthma (in ABPA) 8) brownish plugs in sputum (in ABPA) 9) headaches, seizures, confusion, ocular motor palsies
Characteristic Test Findings
Chest radiograph – 1) focal infiltrates 2) “halo sign” 3) progression of “halo sign” to “crescent sign” over several day period 4) central bronchiectasis Laboratory – 5) eosinophilia > 1000/muL (in ABPA) 6) increased IgE (in ABPA)
Histology/Gross Pathology
1) filamentous fungi with septate hyphae and dichotomous branching 2) vascular invasion leads to thrombosis, necrosis, and infarction 3) positive silver stain
Associated Conditions
increased incidence in – 1) burn wounds 2) transplant patients 3) cystic fibrosis 4) glucocorticoid therapy 5) neutropenia 6) cyclosporine use 7) COPD 8) HIV/AIDS (usually involving other lung symptomatology) 9) tuberculosis 10) sarcoidosis 11) bronchiectasis 12) histoplasmosis 13) acute leukemias
Treatment
1) surgery for removal of fungus balls in lung and sinus (does not respond to drugs) 2) lipid formation amphotericin B in neutropenic or high-risk pateints 3) itraconazole if disease is less severe or indolent
Tips for USMLE
1) halo sign is an infiltrative mass of hyphae surrounded by inflammatory cells that have lower attenuation 2) crescent sign develops when the organisms in the center of the halo die and cavitation and necrosis occur 3) ABPA – marked by asthma, pulmonary infiltrates and central bronchiectasis, eosinophilia, increased IgE, wheal and flare reaction to A. fumigatus, and brownish plugs in sputum 4) fungal balls in lungs are almost always in upper lobes
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