The asteroid bodies of sporotrichosis

Some believe that asteroid bodies (AB) in sporotrichosis are nonspecific and are equivalent to the AB of sarcoidosis and other granulomatous diseases. We studied 25 skin biopsy specimens of sporotrichosis in which AB were demonstrated, ten of them with Sporothrix-positive culture. Immunohistochemistry was performed in paraffin-embedded biopsy specimens using an anti-Sporothrix antibody. The same procedures were done with seven biopsy specimens of lobomycosis, which contained AB within giant cells. These did not react with the anti-Sporothrix antibody, and by electron microscopy they displayed filamentous and myelin figures similar to the AB of sarcoidosis. In sporotrichosis, the AB are extracellular eosinophilic structures, 15-35 microm in diameter, and located within abscesses. One to three are found in a section. They consist of a central yeast, surrounded by eosinophilic spicules. The yeast stains with the anti-Sporothrix antibody, while the spicules do not. Therefore, AB in sporotrichosis are specific for disease. Visualization of the spicules alone can lead to the demonstration of the AB in adjacent sections, and thus is a useful clue in the diagnosis of sporotrichosis. Sporotrichotic AB must not be confused with the intracellular AB seen in giant cells of granulomatous reactions, which are filamentous and myelin figures that contain lipid.