Blastomycosis

Blastomycosis is a fungal disease commonly presenting with flu like symptoms. It is caused by Blastomyces dermatitidis which resides in moist soil in association with decomposing organic materials like wood. ^[1] Lung is the primary organ affected while the skin is also commonly involved in around 20 to 40% of the cases. ^[2]  

Epidemiology

There is worldwide distribution of the disease. Most of the reported cases are from United States, Canada, Africa, Mexico, South America, Middle East and India. A report in 1990s shows a mortality rate of 0-2% in resolved cases of people with intact immune system whereas immunocompetent patients have a striking mortality rate of 29%. Complications are only common in persons with immunosuppression. Most patients reported are within the age range of 30-69 years old with mean age of 45. The disease can occur in extreme of ages- infants and the very old. ^[3]

Causes

Blastomycosis occurs when an individual inhales Blastomyces dermatitidis particles. The fungus is commonly found in moist soil predominantly on rotting vegetation. The fungi enters via the lungs, causes infection and then spreads throughout the body in some cases. ^[4]

Risk Factors

People with weakened immune system such as HIV and organ transplant patients are at greater risk. Human-to-human or animal-to-human transmission is rare. ^[2]

There is greater chance of having the disease by staying around infected soil and males are said to get the disease more than females. ^[4]

Symptoms

Usually, symptoms mimic respiratory illnesses. A flulike illness may occur with the individual presenting with fever, chills, muscle aches and nonproductive cough. This is self-limited hence may go undiagnosed. ^[3] It may also resemble acute illness such as bacterial pneumonia manifesting with high fever, chills, productive cough, chest pain and yellowish brown sputum. In other cases, blastomycosis may conform to chronic illness presentation hence may resemble tuberculosis or lung cancer. The individual may have low grade fever, weight loss, sweats at night and productive cough with sputum that is yellowish brown and may be blood-tinged. In other occasions, the disease may be similar to Acute Respiratory Distress Syndrome (ARDS) wherein the patient will have high fever, rapid breathing and shortness of breath. Blastomycosis also frequently presents with skin lesions that may be found on the face, neck and extremities. ^[2]

Diagnosis

The best way of diagnosing blastomycosis is by doing a fungal culture. ^[1] Patient history coupled with physical exam is also essential.

Treatment

Blastomycosis infection that stays in the lungs may not need medication since the infection may resolve spontaneously. When there is dissemination, treatment is necessary. Antifungal drugs such as itraconazole (mild to moderate) and amphotericin B (severe) are given.^[2]

References:

1.  http://www.cdc.gov/fungal/blastomycosis/

2. http://dermnetnz.org/fungal/blastomycosis.html

3. http://emedicine.medscape.com/article/296870-overview#a0199

4. http://www.nlm.nih.gov/medlineplus/ency/article/000102.htm