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Histoplasmosis

DESCRIPTION: Disease of the choroid; caused by an invasion of a fungal organism; transmitted by airborne spores found in dried animal excrement; the peripheral fundus has "punched-out" spots similar to healed chorioretinal lesions, but smaller and less pigmented. Macular involvement may occur later (believed to be a result of earlier choroidal sensitization and subsequent reinfection); these macular lesions may progress to hemorrhagic detachments. There is no vitreous haze. There is a positive reaction to a skin test for the disease. It seems to occur more often in the eastern half of the United States.

TREATMENT: Many treatments have been advocated, including systemic corticosteroids, antihistamines, and photocoagulation of perimacular leakage, but results have been questionable in all cases. Once disciform changes begin, prognosis is very poor.

IMPLICATIONS: In the initial stages, when only the peripheral fundus is affected, the vision is not affected (except for peripheral scotomas, which do not usually interfere with visual functioning). If the macula becomes involved, decreased central acuity, deficient color vision, and central scotoma can cause considerable loss of visual function. Optical aids may be helpful in these cases.

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