Fungi in the Aspergillus genus can affect the orbit in several distinct clinical entities. Invasive aspergillosis is a fungal disease characterized by fulminant sinus infection with secondary orbital invasion. Patients present with severe periorbital pain, decreased vision, and proptosis. Diagnosis is confirmed by 1 or more biopsies. Grocott-Gomori methenamine–silver nitrate stain shows septate branching hyphae of uniform width (see the discussion of aspergillosis in BCSC Section 5, Neuro-Ophthalmology). Therapy consists of aggressive surgical excision of all infected tissues and administration of antifungal agents, including polyenes (amphotericin B, liposomal amphotericin B), azoles (eg, itraconazole, voriconazole), echinocandins (caspofungin), and pyrimidine analogues (flucytosine), or a combination thereof.
Chronic necrotizing aspergillosis is an indolent infection resulting in slow destruction of the sinuses and adjacent structures. Although the prognosis is much better than that for acute fulminant disease, intraorbital and intracranial extension can still occur and result in significant morbidity.
Chronic, localized noninvasive aspergillosis also involves the sinuses and occurs in immunocompetent patients who may not have a history of atopic disease. Often, there is a history of chronic sinusitis, and the proliferation of fungal organisms results in a tightly packed fungus ball. This type of aspergillosis is characterized by a lack of either inflammation or bone erosion.
Allergic aspergillosis sinusitis occurs in immunocompetent patients with nasal polyposis and chronic sinusitis. Patients may have peripheral eosinophilia; elevated total immunoglobulin E (IgE), fungus-specific IgE, and immunoglobulin G (IgG) levels; or positive skin test results for fungal antigens. CT imaging reveals mottled areas of increased attenuation on nonenhanced images, corresponding to thick allergic mucin within the sinus. Bone erosion and remodeling, while often present, do not signify tissue invasion. MRI may be more specific, showing signal void areas on T2-weighted scans. Sinus biopsy reveals thick, peanut butter–like or green mucus, with histologic examination showing numerous eosinophils, eosinophil degradation products, and extramucosal fungal hyphae. Treatment consists of endoscopic sinus debridement as well as systemic and topical corticosteroids. Up to 17% of patients with allergic fungal sinusitis initially present with orbital signs.
Figure 4-6 Coronal CT scan demonstrates a hydatid cyst of the left inferior rectus muscle.
(Courtesy of Don O. Kikkawa, MD.)
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Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.