Fig. 9.38 (a–b) Fundus photographs show multifocal blastomycosis choroiditis. Biopsy of skin revealed blastomycosis. (Modified and reprinted with permission from

Fig. 9.39 Colony of Blastomyces dermatitidis on moldinhibitory agar (Modified and reprinted with permission from http://www.doctorfungus.org)

Gass JDM. Stereoscopic Atlas of Macular Diseases; Diagnosis and Treatment. 4th ed. St. Louis: Mosby, Inc. 1997)

Fig. 9.40 Granuloma containing Blastomyces dermatitidis

(Reprinted with permission from Lewis H, Aaberg TM, Fary DRB, et al. Latent disseminated blastomycosis with choroidal involvement. Arch Ophthalmol 1988; 106:527–530)

does not colonize, so detection by histologic analysis or culture confirms the diagnosis [54].

B. dermatitidis produces granulomatous reactions with choroidal and retinal involvement (Fig. 9.40). The fungus is identified commonly by microscopy of exudate, sputum, tissue after cell digestion, or aqueous and vitreous aspirates using 10% potassium hydroxide, but fine-needle aspiration cytologic analysis can be used.

Treatment

In addition to amphotericin B and ketoconazole, itraconazole currently is the accepted form of

therapy for blastomycosis. Pars plana vitrectomy together with intravitreous injection of amphotericin B must be performed if significant vitreous inflammation is present.

Sporothrix schenckii Chorioretinitis

Sporothrix schenckii is a saprophytic, dimorphic fungus worldwide. The organism can be found in soil associated with plant organic matter (e.g., thorns, dry leaves, and wood), water,

and decomposing organic matter, among others. Natural infection of rats, dogs, mules, and horses also has been reported [55]. Sporothrix schenckii affects humans in three distinct forms: cutaneous, pulmonary, and disseminated sporotrichosis. Most cases of intraocular involvement of disseminated sporotrichosis have been endophthalmitis, which shows poor response to therapy.

Risk Factors

•Farmers, gardeners, laborers, and certain types of miners [55]

•Renal transplant patients

•Patients with debilitating or immunosuppressive diseases

Pathogenesis

Most cases of sporotrichosis start as primary cutaneous lesions following inoculation with contaminated soil or other vegetable material. This stage is followed by centripetal lymphatic spread, which appears as multiple subcutaneous nodules creeping up an extremity. Intraocular infections may be due to direct extension from the lid or conjunctiva, but most are endogenous, owing to systemic infection, and usually lead to loss of the eye.

Ocular (and other monofocal sites) infections without an antecedent history of trauma or evidence of systemic disease are rare but may be more common with S. schenckii than with other causes of fungal endophthalmitis [56].

Clinical Features

The presenting features of intraocular sporotrichosis are nonspecific and include pain, decreased vision, and redness. Ocular manifestations of sporotrichosis include lesions of the eyelids and lacrimal apparatus, conjunctivitis (Fig. 9.41), keratitis, scleritis, nongranulomatous anterior uveitis with small white keratic precipitates or granulomatous anterior uveitis with iris nodules [57], endophthalmitis, and chorioretinitis that appears as fluffy, white, necrotic retinal lesions with overlying vitreous

Fig. 9.41 Follicular conjunctivitis with conjunctival granuloma secondary to Sporothrix schenckii infection

haze (Fig. 9.42). The condition may progress over several months [58].

Diagnosis

The histopathological diagnosis of S. schenckii is often difficult. In primary lesions, the free yeast forms are rarely found in tissue sections stained with hematoxylin and eosin and may not be identified despite stains with periodic acid Schiff or glyceryl monostearate, making recovery in culture the diagnosis. Repeated aqueous and vitreous aspirates may be necessary to isolate the organism. In patients with other sites of infection, such as skin or joints, biopsy or aspiration of that site, with culture, also may be helpful. In culture it grows in a yeastlike form at incubation temperatures and filamentous form at room temperature. Sabouraud agar is a satisfactory culture medium, in which cream-colored to black leathery colonies develop within 3–5 days [55].

Treatment

For disseminated sporotrichosis or extraocular sporotrichosis, intravenous amphotericin B is usually used. Early vitrectomy and intravitreal injection of amphotericin B in cases of S. schenckii endophthalmitis are important. Also, itraconazole can be used for disseminated and ocular sporotrichosis [59].