What is Blastomycosis?
Blastomycosis is an infection caused by a fungus called Blastomyces dermatitidis. This fungus is mainly found in the soil of certain parts of the United States such as the Ohio and Mississippi River Valleys, Great Lakes region, and southeastern regions. Typically, people contract the infection by inhaling the fungal spores.
In many cases, the infection affects the lungs and might not show any symptoms, making it hard to detect. However, it can occasionally lead to serious and potentially life-threatening breathing problems. About 25% to 30% of the time, the infection can spread from the lungs to other parts of the body, with the skin being the most common site it moves to.
In rare situations, blastomycosis can also affect the skin directly through a wound or injury. It’s worth noting that blastomycosis can infect both people with a weak immune system and those with a healthy immune system.
What Causes Blastomycosis?
Blastomycosis is a disease caused by Blastomyces dermatitidis, a type of fungus. This fungus is part of the Ascomycota group, and belongs to the family Agellomycetaceae. It’s also known as Ajellomyces dermatitidis in its asexual state. Just like how humans have different states, like a baby or an adult, so do fungi. Blastomyces dermatitidis has two states it can exist in.
When the temperature is around 77 degrees Fahrenheit (25 Celsius), it takes on a mold form that looks like fluffy white mold. But if the temperature goes up to 98.6 degrees Fahrenheit (37 Celsius), it changes into a yeast form that looks like brown folded bread yeast.
This fungus can be found in the soil, where it digs into the surface and spreads out, similar to how roots of a plant grow. It produces offspring through a process called asexual reproduction, creating small spores that are between 2-10 micrometers in size.
In cells that are infected with this fungus, Blastomyces dermatitidis looks like budding yeast cells, and are quite large – about 8 to 10 micrometers in size.
Risk Factors and Frequency for Blastomycosis
Blastomycosis is a disease that is most commonly found in certain parts of the United States, including the Ohio and Mississippi River valleys, areas near the Great Lakes, and the southeast. Most years, there are fewer than 1 case per 100,000 people in states where the disease is common, such as Mississippi, Kentucky, Arkansas, and Wisconsin. Other states where the disease often appears include North Carolina, Tennessee, Louisiana, and Illinois.
Anyone can get blastomycosis, regardless of their age, race, or gender. However, men are slightly more likely to get the disease. This likelihood is usually attributed to the types of activities men typically engage in at work or for fun. Adult men, in particular, are more prone to developing a system-wide infection.
Signs and Symptoms of Blastomycosis
Blastomycosis is a condition that often starts with symptoms similar to the flu. These symptoms can be mild and usually disappear within a few days, so they might not be noticed or diagnosed. Furthermore, around 50% of the people who get infected with blastomycosis do not show any symptoms. This disease can cause acute or chronic pneumonia and in some severe cases, especially among the elderly or people with a weaker immune system, it may lead to a serious condition called acute respiratory distress syndrome.
If the fungus causing blastomycosis spreads to other parts of the body outside the lungs, it can result in more symptoms. The skin is often affected first, showing signs like small raised spots that evolve into crusty areas often with a clear center or an open sore. There could be swelling in the lymphatic system and lymph nodes. In about 25% of these serious cases, the disease can affect the bones, leading to bone damage. Even though this can happen to any bone, it most commonly affects the lower spine and pelvis.
In addition, blastomycosis can cause inflammation in the prostate, testicles or the epididymis, which is the tube that carries sperm. In 5% to 10% of serious blastomycosis cases, the central nervous system is involved, leading to conditions like meningitis and abscesses in the brain or spinal cord.
- Flu-like symptoms
- No symptoms in about 50% of cases
- Acute or chronic pneumonia
- Acute respiratory distress syndrome in severe cases
- Skin symptoms starting as small raised spots that evolve into crusty areas often with a clear center or an open sore
- Swelling in the lymphatic system and lymph nodes
- Bone damage, especially in the lower spine and pelvis
- Inflammation in the prostate, testicles or the epididymis
- Central nervous system complications like meningitis and abscesses in the brain or spinal cord in 5% to 10% of serious cases
Testing for Blastomycosis
To diagnose a certain fungal infection known as Blastomyces dermatitidis, the fungus itself must be seen clearly. To do this, doctors often collect a sample of sputum – the mucus from your lungs that you might cough up. Doctors then stain this sample with a special substance, like 10% potassium hydroxide or a fungal stain. This process is about 80% successful in detecting the fungus.
Another method involves taking a small sample of skin lesions for examination. During this examination, doctors are looking for changes in the skin cells, specifically pseudoepitheliomatous hyperplasia, which is an abnormal growth of the skin’s top layer, and neutrophilic abscesses, which are areas filled with pus. Sometimes, these yeasts can be hard to spot as they often hide within immune cells called histiocytes or within areas of skin infection. These yeasts are microscopic, about 8 to 15 micrometers wide, with thick double-layered walls and a unique budding pattern.
Cultures, which is a way of growing the fungus in a laboratory, is the most sensitive method for detecting this kind of yeast infection. Usually, growth is observed within 5 to 10 days. But in cases where there are only a few organisms present in the specimen, detection may take up to 30 days.
You might also have a chest X-ray or other imaging to check if the lungs are affected. However, these images can vary greatly and aren’t specific, which means they don’t conclusively establish the presence of blastomycosis. In fact, it can often look like lung cancer on an X-ray.
If the doctor suspects the fungus may have spread to your central nervous system (the brain and spinal cord), you might have a lumbar puncture. This is a procedure where a needle is inserted into the lower part of your spine to collect fluid for testing. However, it can be difficult to diagnose this condition conclusively with this method.
Lastly, a specific test using a “chemiluminescent DNA probe” is available. This is a special procedure that identifies the DNA of the fungus and can give results within several hours. However, it may also give a positive result for another related fungus found mostly in South and Central America, known as Paracoccidioides brasiliensis.
Treatment Options for Blastomycosis
Even though spontaneous recovery could happen in some cases, treatment is generally recommended for everyone with mild to moderate illness to prevent the disease from spreading and recurring. Itraconazole, a type of antifungal medication, is often the first choice of treatment for all forms of this disease, unless the condition is severe or life-threatening. This medicine helps to fight off the infection effectively and usually has low toxicity or harm to the body. However, keep in mind that its absorption depends on stomach acid.
There are other antifungal medicines such as ketoconazole and fluconazole that can be used as well but they are not the first pick because they may not work as well and in some cases can have more side effects. Voriconazole, another antifungal medicine, is especially handy for infections affecting the central nervous system (CNS), which includes the brain and spinal cord. Keep in mind that these antifungal medicines cannot be used during pregnancy.
Severe, life-threatening cases often require the use of a powerful antifungal medication called amphotericin B. This medicine can be given in its traditional form or as a lipid formulation called liposomal amphotericin B. The latter is typically preferred for treating severe infections and when the condition has spread to the CNS, or for managing the illness in pregnant women. This is because the lipid formulation is less likely to cause kidney damage, a known side effect of amphotericin B. This medicine can also cause other side effects such as low potassium levels, anemia, fever, chills, nausea, and inflammation of the vein at the site where it is injected.
What else can Blastomycosis be?
Blastomycosis is a condition that can sometimes be mistaken for other conditions. These include:
- Pneumonia
- Tuberculosis
- Non-infectious pulmonary disease
- Cancer
What to expect with Blastomycosis
Patients with a healthy immune system generally have a good outlook as they have a lower risk of suffering from complications of the infection. In fact, successful treatment of this condition happens in about 80% to 95% of these cases.
However, patients with a weakened immune system who get Blastomycosis, a fungal infection, usually have a poorer outlook.
Possible Complications When Diagnosed with Blastomycosis
Possible problems that may arise include:
- The disease coming back (relapse/recurrence)
- Pockets of pus (abscesses)
- Sores on the skin
- Negative reactions to the treatment (amphotericin)
Preventing Blastomycosis
Patients with weakened immune systems should be advised to steer clear of places and activities that are known to increase the risk of getting an infection. It’s key for these individuals to understand how they can protect themselves better and reduce their chances of getting sick.
