Blastomycosis

Abstract

Blastomycosis is a systemic pyogranulomatous infection caused by the thermally dimorphic fungus Blastomyces dermatitidis. The annual incidence in endemic areas is estimated to be less than 1 case per 100,000 people. Original infection occurs after the inhalation of conidia (spores), resulting in a pulmonary disease after a 3–6-week incubation period. Extrapulmonary disease occurs in up to 40% of patients. Ophthalmic infections are rare and require prompt diagnosis, as untreated infections can result in rapid and complete vision loss. The diagnosis requires a biopsy or culture of affected tissues, and microscopic examination can reveal yeast forms with characteristic broad-based budding and granulomatous changes. The most common ocular manifestations are that of uveitis – specifically iridocyclitis, choroiditis, endophthalmitis, and panophthalmitis. Common symptoms include photophobia, decreased visual acuity, and visual field deficits. Anterior segment findings include corneal opacification, anterior chamber reaction, iris mass or abscess, and clouding of the lens. Funduscopic examination can reveal vitreous haze and yellow or yellow-white elevated choroidal lesions that can range from 0.125 to 8 disc diameters in size. Diagnostic evaluation may include echography, fluorescein angiography, and imaging of the orbits. Ancillary testing should include imaging to evaluate for pulmonary lesions. Current standard of care relies on local therapy and systemic antifungals, including oral azoles and intravenous amphotericin B for any patient with central nervous system (CNS) involvement.