Blastomycosis

Blastomycosis

Blastomycosis
Microscopic image of Blastomyces dermatitidis
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Overview

Blastomycosis is a fungal infection caused by the dimorphic fungus Blastomyces dermatitidis. It primarily affects the lungs but can disseminate to other parts of the body, including the skin, bones, and central nervous system. The disease is endemic in certain regions of North America, particularly in the Ohio and Mississippi River valleys, the Great Lakes region, and parts of Canada.

Etiology

The causative agent of blastomycosis is Blastomyces dermatitidis, a fungus that exists in two forms: a mold form in the environment and a yeast form in the human body. The fungus is found in moist soil and decaying organic matter, such as wood and leaves.

Pathophysiology

Inhalation of the conidia (spores) of Blastomyces dermatitidis leads to infection. Once inhaled, the spores transform into yeast forms in the alveoli of the lungs. The yeast can evade the immune system and multiply, leading to pulmonary infection. In some cases, the infection can spread hematogenously to other organs.

Clinical Manifestations

The clinical presentation of blastomycosis can vary widely. Common symptoms include:

• Fever
• Cough
• Night sweats
• Muscle aches
• Joint pain
• Chest pain

In cases of disseminated disease, patients may present with skin lesions, osteomyelitis, or meningitis.

Diagnosis

Diagnosis of blastomycosis is based on clinical suspicion, especially in patients with a history of exposure in endemic areas. Diagnostic methods include:

• Culture of the organism from clinical specimens
• Histopathology showing broad-based budding yeast
• Antigen detection in urine or serum

Treatment

The primary treatment for blastomycosis is antifungal therapy. The choice of medication depends on the severity of the disease:

• Itraconazole is the drug of choice for mild to moderate disease.
• Amphotericin B is used for severe or disseminated cases.

Prognosis

With appropriate treatment, the prognosis for blastomycosis is generally good. However, untreated or severe cases can lead to significant morbidity and mortality.

Prevention

Preventive measures include avoiding activities that disturb soil in endemic areas, especially for immunocompromised individuals. There is currently no vaccine available for blastomycosis.

Epidemiology

Blastomycosis is considered a rare disease, with most cases occurring in North America. The incidence is higher in males and in individuals with occupational or recreational exposure to wooded or moist environments.

See Also

• Fungal infections
• Dimorphic fungi
• Pulmonary infections

External Links

• [CDC - Blastomycosis](https://www.cdc.gov/fungal/diseases/blastomycosis/index.html)
• [Infectious Disease Society of America - Blastomycosis Guidelines](https://www.idsociety.org/)