Abstract
Purpose: :
To review clinical and morphological characteristics of 16 cases of feline ocular histoplasmosis and 8 suspected cases of histoplasmosis where no organisms were found.
Methods: :
Cases were retrieved from the archive of the Comparative Ocular pathology Laboratory of Wisconsin. Cases were stained by H&E and Gomori silver stain. Epidemiologic and clinical data and histological features were recorded.
Results: :
Of the 24 cases 16 were diagnosed as ocular histoplasmosis. 8 cases had no organisms but histological characteristics resembling POHS. Ages of affected cats ranged from 1.5 to 16 years (average 7.2). 4 of the Histoplasma positive cases presented bilateral ocular involvement, 9 only OD, 2 only OS and 1 case only conjunctival involvement. Of the 8 cases with no detectable organisms, 6 were OS and 2 were OD. A lymphoplasmacytic and granulomatous pan-uveitis more prominent in the choroid with pyogranulomatous endophthalmitis and retinal and choroidal intra-histiocytic fungal yeasts was the most common histological features of the positive cases. The negative cases presented a lymphoplasmacytic and granulomatous choroiditis with fibrovascular proliferation involving choroid, RPE and outer retina. 81.3% of the Histoplasma-positive cases also had choroidal neovascularization. 43.8% of the positive animals and 37.5% of the negative animals presented systemic clinical signs. 87.5% of the ocular histoplasmosis and 38% of the suspected histoplasmosis cases occurred in mid south and west (OH, MO) and central (KS, OK, TX) states.
Conclusions: :
FOH is characterized by lymphoplasmacytic and granulomatous panuveitis and pyogranulomatous endophthalmitis with intra-histiocytic retinal and choroidal yeasts affecting mid-age animals in endemic areas. Suspected histoplasmosis cases present no organisms and histological lesions similar to cats with organisms and human POHS (choroidal neovascularization and moderate lymphoplasmacytic infiltrate). We speculate that the cat is a useful model to study the mechanisms involved in the development of POHS.
Keywords: choroid: neovascularization • fungal disease • pathobiology