HISTOPLASMOSIS IN THE SKIN AND GINGIVA IN A DOG

An 8-year-old, female mongrel dog had granulomatcus lesions in the sku ll skin and gingiva of the left mandible. The lesions were macroscopic ally seen as grayish white papular granulomas, and microscopically con sisted of numerous swollen macrophages and a few neutrophils without f ibrocaseous necrosis. Macrophages contained many small oval or round-s haped yeast-like cells and a few rod-shaped organisms indicating a nar row based budding in their cytoplasm. The yeast-like cells were 2-5 mu m (average 3.5 mu m) in diameter, and appeared as a central, spherica l, lightly basophilic body surrounded by a clear zone or ''halo''. The cell wall and central body were stained by the periodic acid-Shiff, G rocott's methenamine silver impregnation, or Gridley fungus method. Im munohistochemically, yeast-like cells were positive to anti-histoplasm a yeast antibody, and rod-shaped organisms were positive to anti-histo plasma mycelial antibody. The present paper describes the first case o f canine histoplasmosis in Japan.