have CNS involvement and present as brain abscess, epidural abscess or meningitis. Blastomycosis in non-lung organs such as the skin may present a very wide range of symptoms, including the following: skin lesions, which may be verrucous (wart-like) or ulcerated with small pustules at the margins. bone or joint pain due to bone lytic lesions. pain when urinating due to prostatitis. hoarseness due to laryngeal involvement. headache, confusion or other neurological symptoms caused by central nervous system involvement. Cause Blastomycosis is caused by dimorphic fungi in the genus Blastomyces, in the phylum Ascomycota and family Ajellomycetaceae. In eastern North America, the most common cause of blastomycosis is Blastomyces dermatitidis, but Blastomyces gilchristii has been associated with some outbreaks. In western North America, many cases of blastomycosis are caused by Blastomyces helicus, which most commonly attacks immunodeficient people and domestic animals. The species Blastomyces percursus causes many cases of blastomycosis in Africa and the Middle East. In Africa, blastomycosis may also be caused by Blastomyces emzantsi, which is often associated with infections outside the lungs. In endemic areas, Blastomyces dermatitidis lives in soil and rotten wood near lakes and rivers. Although it has never been directly observed growing in nature, it is thought to grow there as a cottony white mold, similar to the growth seen in artificial culture at 25 °C. The moist, acidic soil in the surrounding woodland harbors the fungus. Pathogenesis Inhaled conidia of Blastomyces are phagocytosed by neutrophils and macrophages in alveoli. Some of these escape phagocytosis and transform into yeast phase rapidly. Having thick walls, these are resistant to phagocytosis. Once they have transitioned to the yeast phase, the Blastomyces cells express the protein BAD-1, which helps the yeast cells attach to host cells, and also impairs activation of immune cells while inhibiting release of tumor necrosis factor. In lung tissue, the cells multiply and may also disseminate through blood and lymphatics to other organs, including the skin, bone, genitourinary tract, and brain. The incubation period for pulmonary blastomycosis is 3 to 15 weeks, although 30–50% of infections are asymptomatic. Diagnosis Because the symptoms of blastomycosis resemble those of many other conditions, including tuberculosis and lung cancer, diagnosis is often delayed. In 40% of cases, the diagnosis takes more than a month. A rapid diagnosis can however be made based on microscopic examination of sputum samples or samples obtained from a tissue biopsy or bronchoalveolar lavage.