What is Blastomycosis?

Blastomycosis is a rare infectious condition caused by a fungus known as Blastomyces dermatitidis. It manifests as a lung infection that can be asymptomatic or cause life-threatening problems such as acute respiratory distress syndrome. The symptoms vary widely depending on which organ system is damaged. The lungs and skin are the most commonly damaged organs during the chronic phase of the disease.

Blastomyces dermatitidis fungi

Image Credit: Kateryna Kon/Shutterstock.com

Causes and Symptoms

Blastomyces dermatitidis is found in soils in the Great Lakes region, Ohio and Mississippi River Valleys, and the south-eastern United States. Blastomyces dermatitidis thrives in damp soil and decomposing debris like wood and leaves. Mold spores spread the fungus. The fungus infects the lungs by converting to yeast and is carried around the body by the blood. People with a weakened immune system are more susceptible to blastomycosis.

Fever, headaches, chest pain, chills, weight loss, cough, night sweats, and difficulty breathing are the common symptoms of blastomycosis (dyspnea). Even when they are diseased, some people do not show any of these symptoms (asymptomatic). Muscle and joint discomfort might develop during the acute period and lasts for nearly three weeks on average. The infection may clear up on its own or develop into a persistent infection. Chronic blastomycosis can impair the lungs, bones, skin, genitourinary tract, and central nervous system if it lasts more than three weeks.

The symptoms usually occur 2 weeks to 15 months after a person inhales the fungus spores. Skin involvement is particularly common in people who have blastomycosis. Verrucous (wart-like) and papulopustular (small elevated pus-filled) lesions are prevalent. They may be violet in color and contain little abscesses around the edges of the lesions. Nodular lesions can develop beneath the skin (subcutaneous) and are generally present along with a pulmonary fungal infection.

Blastomycosis frequently manifests itself as persistent pneumonia when it affects the lungs, which are common sites of fungal involvement. Cough with thick sputum, trouble breathing, chest pain, and/or a quick heartbeat are all possible symptoms. Respiratory Distress Syndrome, characterized by hyperventilation and hypoxemia, can develop in some patients with severe cases of blastomycosis. 

The earliest symptoms of blastomycosis are flu-like and usually fade away within a few days, though the infection may remain untreated due to its mild nature. Furthermore, approximately 50% of all infected people are asymptomatic. Acute or chronic pneumonia can occur, and acute respiratory distress syndrome can develop in elderly or immunocompromised people. Extrapulmonary illness can develop when Blastomyces dermatitidis has spread to other organs, with the skin being the most prevalent location of infection. 

Cutaneous blastomycosis clinically manifests as papules that progress to vegetative plaques with center clearing or ulceration. Lymphangitis and lymphadenopathy are possible symptoms. Bone lesions, which occur in 25% of extrapulmonary cases and are frequently lytic, are the second most prevalent finding. Though osteomyelitis can infect any bone, it is most typically found in the lower spine and pelvis. Prostatitis, orchitis, and epididymitis are examples of extrapulmonary illness symptoms. 

Epidemiology

In 5% to 10% of instances, the central nervous system is implicated, including cases of meningitis and intracranial or epidural abscesses. Blastomycosis is found throughout the Ohio and Mississippi River valleys, the Great Lakes region, and the south-eastern United States. In the frequently impacted states of Mississippi, Kentucky, Arkansas, and Wisconsin, the annual incidence is less than 1 case per 100,000 persons. North Carolina, Tennessee, Louisiana, and Illinois are among the states that are frequently affected. It is considerably prevalent in the neighboring regions of Canada as well.

Diagnosis and Treatment

For a conclusive diagnosis, direct imaging of Blastomyces dermatitides is required. The yield of sputum specimens stained with 10% potassium hydroxide or a fungal stain is approximately 80%. Pseudoepitheliomatous hyperplasia with neutrophilic abscesses is shown by biopsy and histological investigation of skin lesions. The use of chest radiologic imaging to screen for pulmonary involvement is possible, however, the results are varied and lack specificity.

On lung radiography, blastomycosis is the most likely of all the systemic fungal conditions to look like cancer. Pulmonary blastomycosis can be misdiagnosed as a cancerous condition such as lung cancer. To confirm the diagnosis of blastomycosis, a specific instrument (bronchoscopy) may be used to examine the throat. Cutaneous blastomycosis of the skin might resemble skin cancer in some cases.

Although spontaneous remission is possible, all patients with mild or moderate disease should be treated to prevent spread and recurrence. Except in severe, life-threatening situations, itraconazole is the preferred treatment for all forms of the condition. Itraconazole has low toxicity and strong efficacy, but it's vital to remember that it needs gastric acidity to be absorbed. 

Other azoles, such as ketoconazole and fluconazole, can be used but are less effective. Voriconazole has a high level of penetration into the cerebrospinal fluid and consequently has a function in CNS illness. For severe blastomycosis in the lungs or infections that have spread to other regions of the body, amphotericin B is frequently prescribed. Treatment might last anywhere from six months to a year, depending on the severity of the infection and the person's immune state.

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Further Reading


Last Updated: Jan 24, 2022

Emily Henderson

Written by

Emily Henderson

During her time at AZoNetwork, Emily has interviewed over 300 leading experts in all areas of science and healthcare including the World Health Organization and the United Nations. She loves being at the forefront of exciting new research and sharing science stories with thought leaders all over the world.

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