called "the great pretender". Many cases are asymptomatic or subclinical. Lung symptoms are common, because the lungs are infected in 79% of blastomycosis cases. However, in 25-40% of cases the disease also disseminates to other organs, including the skin. The extent and severity of symptoms depends in part on a person's immune status; less than 50% of healthy people with blastomycosis have symptoms, while immunocompromised patients are especially likely to have the disease spread beyond the lungs to other organs like the skin and bones. Blastomycosis manifests as a primary lung infection in about 79% of cases. The onset is relatively slow and symptoms are suggestive of bacterial pneumonia, often leading to initial treatment with antibacterials. Because the symptoms are variable and nonspecific, blastomycosis is often not even considered in differential diagnosis until antibacterial treatment has failed, unless there are known risk factors or skin lesions. The disease may be misdiagnosed as a carcinoma, leading in some cases to surgical removal of the affected tissue. Upper lung lobes are involved somewhat more frequently than lower lobes. If untreated, many cases progress over a period of months to years to become disseminated blastomycosis. Blastomycosis in the lungs may present a variety of symptoms, or no symptoms at all. If symptoms are present they may range from mild pneumonia resembling a pneumococcal infection to acute respiratory distress syndrome (ARDS). Common symptoms include fever, chills, headache, coughing, difficulty breathing, chest pain, and malaise. Without treatment, cases may progress to chronic pneumonia or ARDS. ARDS is an uncommon but dangerous manifestation of blastomycosis. It was seen in 9 of 72 blastomycosis cases studied in northeast Tennessee. Such cases may follow massive exposure, such during brush clearing operations. In the Tennessee study, the fatality rate was 89% in the ARDS cases, but only 10% in the non-ARDS cases. In disseminated blastomycosis, the large Blastomyces yeast cells translocate from the lungs and are trapped in capillary beds elsewhere in the body, where they cause lesions. The skin is the most common organ affected, being the site of lesions in approximately 60% of cases. The signature image of blastomycosis in textbooks is the indolent, verrucous or ulcerated dermal lesion seen in disseminated disease. Osteomyelitis is also common (12–60% of cases). Other recurring sites of dissemination are the genitourinary tract (kidney, prostate, epididymis; collectively ca. 25% of cases) and the brain (3–10% of cases). 40% of immunocompromised individuals