22.4 Respiratory mycoses  (Page 3/11)

Blastomycosis

Blastomycosis is a rare disease caused by another dimorphic fungus, Blastomyces dermatitidis . Like Histoplasma and Coccidioides , Blastomyces uses the soil as a reservoir, and fungal spores can be inhaled from disturbed soil. The pulmonary form of blastomycosis generally causes mild flu-like symptoms and is self-limiting. It can, however, become disseminated in immunocompromised people, leading to chronic cutaneous disease with subcutaneous lesions on the face and hands ( [link] ). These skin lesions eventually become crusty and discolored and can result in deforming scars. Systemic blastomycosis is rare, but if left untreated, it is always fatal.

Preliminary diagnosis of pulmonary blastomycosis can be made by observing the characteristic budding yeast forms in sputum samples. Commercially available urine antigen tests are now also available. Additional confirmatory tests include serological assays such as immunodiffusion tests or EIA. Most cases of blastomycosis respond well to amphotericin B or ketoconazole treatments.

Watch this profile of a blastomycosis lung infection.

Mucormycosis

A variety of fungi in the order Mucorales cause mucormycosis , a rare fungal disease. These include bread molds, like Rhizopus and Mucor ; the most commonly associated species is Rhizopus arrhizus (oryzae) (see [link] ). These fungi can colonize many different tissues in immunocompromised patients, but often infect the skin, sinuses, or the lungs.

Although most people are regularly exposed to the causative agents of mucormycosis, infections in healthy individuals are rare. Exposure to spores from the environment typically occurs through inhalation, but the spores can also infect the skin through a wound or the gastrointestinal tract if ingested. Respiratory mucormycosis primarily affects immunocompromised individuals, such as patients with cancer or those who have had a transplant. Centers for Disease Control and Prevention. “Fungal Diseases. Definition of Mucormycosis.” 2015 http://www.cdc.gov/fungal/diseases/mucormycosis/definition.html. Accessed July 7, 2016.

After the spores are inhaled, the fungi grow by extending hyphae into the host’s tissues. Infections can occur in both the upper and lower respiratory tracts. Rhinocerebral mucormycosis is an infection of the sinuses and brain; symptoms include headache, fever, facial swelling, congestion, and tissue necrosis causing black lesions in the oral cavity. Pulmonary mucormycosis is an infection of the lungs; symptoms include fever, cough, chest pain, and shortness of breath. In severe cases, infections may become disseminated and involve the central nervous system, leading to coma and death. Centers for Disease Control and Prevention. “Fungal Diseases. Symptoms of Mucormycosis.” 2015 http://www.cdc.gov/fungal/diseases/mucormycosis/symptoms.html. Accessed July 7, 2016.