The gross photo shows a lung severely infected with Blastomyces dermatitidis, a fungus. Histologically (right photo), one sees a granuloma with central neutrophils. The macrophages fail to kill the organisms; neutrophils continue to be called into action. The lesions are referred to as suppurative granulomas.
The organism enters the body via inhalation of spores which became airborne from contaminated soil. In the lungs the spores transform to yeast forms. The organisms may enter blood and lymphatic vessels. The most common extrapulmonary sites of infection are skin, bone, genitourinary tract, brain, and meminges.
The yeast form as seen in tissue sections using various stained; (left to right) H&E, silver, and PAS. Broad-based budding (not shown) is helpful in identifying the organism.
50% of those exposed are asymptomatic. The symptomatic are likely to have a flu-like illness with fever, chills, productive cough, myalgia, arthralgia, and pleuritic chest pain. Chronic pulmonary infection or widespread disseminated infection can follow acute lung infection.