Blastomyces dermatitidis fungus, computer illustration. This fungus is the causative agent of the disease blastomycosis, which has a range of presentations. It mainly affects the lungs and may cause a flu-like disease, an acute disease similar to pneumonia, a chronic illness similar to tuberculosis or the potentially fatal acute respiratory distress syndrome. In some cases it can spread to the skin, bones or organs, causing lesions. Treatment is with antifungal drugs.