Illustration of blastomycosis infection in the lungs, resembling a hidden fungal network.

Blastomycosis: When a TB Diagnosis Misses a Deadly Fungal Infection

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Lena Voss in Health & Wellness October 2026 • 4 min read.

"A Chicago man's journey from misdiagnosis to recovery highlights the challenges and importance of accurate fungal infection detection."


Imagine battling a persistent cough, fever, and unexplained weight loss, only to be told you have tuberculosis (TB). You begin treatment, but your condition doesn't improve. This was the reality for a 36-year-old man from Chicago, whose initial diagnosis of TB masked a far more insidious threat: disseminated blastomycosis.

Blastomycosis is a fungal infection caused by Blastomyces species. While endemic to regions like the Mississippi, Ohio, and St. Lawrence River valleys, and the Great Lakes area, it can occur worldwide. The fungus typically enters the body through the lungs, but it can spread to other organs, including the bones, skin, and central nervous system. This ability to mimic other diseases makes blastomycosis a diagnostic challenge.

The case of the Chicago man underscores the critical importance of considering blastomycosis in patients presenting with respiratory symptoms, especially in endemic regions. His journey from misdiagnosis to eventual recovery offers valuable insights into the challenges and potential pitfalls of diagnosing this elusive fungal infection.

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Who Is Affected

Blastomycosis is a lung infection caused by breathing spores from Blastomyces, a fungus found in soil in some areas. The CDC reports that about half of people infected with Blastomyces develop symptoms, which can include fever, shortness of breath, and cough. People with weakened immune systems are at risk for severe infections, and the illness can sometimes spread beyond the lungs to other parts of the body.

Diagnosis and Treatment

Standard clinical management of blastomycosis involves evaluating its causes, symptoms, diagnosis, and treatment options. Medical News Today describes blastomycosis as a rare fungal infection and reviews available treatment approaches alongside diagnostic considerations. The supplied source does not specify particular tests, drugs, or limitations of accepted methods, so those details cannot be established here.

A Disease With Multiple Names

Blastomycosis is also known as Gilchrist's disease. The supplied material identifies it as a fungal infection that typically affects the lungs. It does not provide dates, milestones, or details about the foundational discoveries that shaped understanding of the disease.

The Case: A Diagnostic Odyssey

Illustration of blastomycosis infection in the lungs, resembling a hidden fungal network.

The 36-year-old Hispanic patient initially presented with right arm weakness and tingling, along with a persistent cough, blood-streaked sputum, fever, and recent weight loss. Two months prior, he had been diagnosed with pulmonary TB at an outside hospital after experiencing hemoptysis and night sweats. Despite denying any TB exposure, travel, or contact with sick individuals, he was started on standard TB treatment.

However, his condition did not improve. Upon admission to another hospital, a chest X-ray revealed a dense consolidation in his right upper lung. A computed tomography (CT) scan confirmed a 9.2 cm mass in the same area. Further complicating the picture, a magnetic resonance imaging (MRI) of the brain showed small enhancing lesions in the right frontal cortex, left cerebellar hemisphere, and upper cervical cord. Despite these findings, initial sputum cultures were negative for bacteria, fungi, and mycobacteria.

  • Initial Misdiagnosis: The patient's symptoms initially led to a diagnosis of pulmonary tuberculosis (TB).
  • Persistent Symptoms: Despite TB treatment, symptoms like cough, fever, and weight loss persisted.
  • Brain Lesions: MRI revealed lesions in the brain, complicating the diagnostic picture.
  • Negative Sputum Cultures: Initial tests failed to identify any bacteria, fungi, or mycobacteria.
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Evidence Still Developing

The supplied material does not identify a recent research study, review, dataset, or clinical trial focused on blastomycosis. A fuller account of current research would require sources describing newer diagnostic, treatment, or prevention findings. No specific research conclusion can therefore be stated from the available material.

Limits of the Available Record

The supplied material does not document a specific failed diagnostic strategy, treatment failure, or counterargument about blastomycosis. It does indicate that the infection can cause symptoms resembling a flu-like illness and can sometimes spread to other body parts. More detailed analysis of diagnostic misses would require sources addressing those failures directly.

A Distinct Fungal Infection

The supplied material characterizes blastomycosis as a fungal infection caused by breathing in Blastomyces from soil. It does not provide a direct comparison with tuberculosis or other lung diseases. Any comparison of symptoms, testing, treatments, or outcomes would therefore require additional sources.

Ultimately, a broncho-alveolar lavage (BAL) confirmed the presence of Blastomyces spp., leading to the correct diagnosis. The patient's TB treatment was discontinued, and he was started on intravenous liposomal Amphotericin B, followed by oral Itraconazole. After two months, he was asymptomatic, and follow-up imaging showed significant resolution of the lesions. He remained symptom-free after nearly a year.

The Takeaway: Think Fungal!

This case underscores the importance of considering blastomycosis in the differential diagnosis of patients presenting with respiratory and neurological symptoms, especially in endemic areas. Early diagnosis and appropriate treatment can prevent disease progression and improve patient outcomes. When symptoms persist despite initial treatment, it's crucial to consider less common infections like blastomycosis and pursue further diagnostic testing.

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Recognizing the Pattern

Taken together, the supplied material describes blastomycosis as a soil-associated fungal lung infection that may produce fever, shortness of breath, and cough. About half of infected people reportedly develop symptoms, while weakened immunity is associated with risk for severe disease. The material does not include independent expert commentary or a source-supported clinical synthesis beyond those points.

Questions for Future Work

The supplied material does not identify specific future studies, emerging therapies, or next-generation diagnostic tools for blastomycosis. Future work could clarify these areas, but the available sources do not support predictions about particular technologies or research directions. Any projected outlook should therefore be treated as uncertain without additional evidence.

Geography and Awareness

Blastomycosis is associated with Blastomyces found in soil in some areas and commonly affects people in certain parts of the United States. This geographic pattern may make recognition more dependent on awareness of local exposure and disease possibilities. The supplied material does not provide evidence about healthcare access, surveillance, diagnostic capacity, or other systemic challenges.

From Symptoms to Severity

For affected people, blastomycosis may begin with fever, shortness of breath, cough, or flu-like symptoms. The infection sometimes spreads to other parts of the body, and people with weakened immune systems face a risk of severe infection. The supplied material does not describe individual patient experiences, costs, or effects on daily life.

What diagnostic timing and test performance mean

  • 31 daysIn the Minnesota surveillance report, the median total time to diagnosis was 31 days, with a wide range from 0 to 1,130 days.[1]
  • 80.8 % sensitivityUrine antigen testing had 80.8% sensitivity in the cited cohort comparison, relative to serology; the excerpt does not give serology's sensitivity.[2]

What the diagnostic evidence adds

The two surveillance summaries describe diagnosis as a process that can take substantially different amounts of time across patients. Their medians are similar, but the long ranges show that the typical interval does not capture every patient's experience.[1] [3]

The test comparison favors urine antigen over serology for sensitivity in the reported cohort, while the broader testing context shows that performance and speed are not the same thing: culture can take weeks, and antigen testing can involve a reference-laboratory delay.[2] [4]

The pooled mortality estimate summarizes evidence across studies, but the reported heterogeneity means it should not be read as a uniform outcome across settings.[5]

How diagnostic measures and study scope compare

In a retrospective chart review of pulmonary cases in Minnesota and western Wisconsin, culture sensitivity was reported as lower than antigen EIA sensitivity, while culture growth could take up to five weeks and EIA results could be delayed by reference-laboratory processing.[4]

The EIA result is not specific to Blastomyces alone in the cited context: the assay targets a fungal cell-wall component that can cross-react with several other fungi. That limits what a positive result by itself establishes.[4]

The retrospective review excluded cases because of coding errors, incomplete charts, or extra-pulmonary presentations, so its analyzed group does not represent every potentially relevant case in the records.[4]

What remains unresolved about these measures

  • How often cross-reactivity changes clinical interpretation is not established by the assay description, which identifies potential cross-reactions but does not quantify their consequences.[4]
  • The mortality synthesis leaves open how much pooled risk varies by setting, because the review reports substantial heterogeneity and notes inconsistent mortality definitions.[5]

Questions about blastomycosis testing

What does CDC guidance say about urine antigen testing?

CDC guidance says urine antigen EIA may offer the highest sensitivity among noninvasive tests and a quick turnaround time.[6]

Sources

  1. Blastomycosis in Minnesota, USA, 1999–2018 - Volume 26, Number 5—May 2020 - Emerging Infectious Diseases journal - CDCCenters for Disease Control and Prevention. CDC twenty four seven. Saving Lives, P (wwwnc.cdc.gov)
  2. Diagnostic Methods and Risk Factors for Severe Disease and Mortality in Blastomycosis: A Retrospective Cohort Study (pmc.ncbi.nlm.nih.gov)
  3. Blastomycosis Surveillance in 5 States, United States, 1987–2018 - Volume 27, Number 4—April 2021 - Emerging Infectious Diseases journal - CDCCenters for Disease Control and Prevention. CDC twenty fou (wwwnc.cdc.gov)
  4. Diagnostic Delay and Antibiotic Overuse in Acute Pulmonary Blastomycosis (pmc.ncbi.nlm.nih.gov)
  5. Mortality associated with Blastomyces dermatitidis infection: A systematic review of the literature and meta-analysis. (pubmed.ncbi.nlm.nih.gov)
  6. Testing Algorithm for Blastomycosis | Blastomycosis | CDC (cdc.gov)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

What is Blastomycosis, and how does it differ from Tuberculosis (TB)?

Blastomycosis is a fungal infection caused by the Blastomyces species. It primarily affects the lungs, but can spread to other parts of the body. Unlike Tuberculosis (TB), which is a bacterial infection, Blastomycosis is caused by a fungus. Both can present with similar respiratory symptoms like cough and fever, which can lead to misdiagnosis. A key difference lies in the causative agent and the treatment required; TB is treated with antibiotics, while Blastomycosis requires antifungal medications such as Amphotericin B and Itraconazole.

2

What are the key symptoms and risk factors associated with Blastomycosis?

Common symptoms of Blastomycosis include persistent cough, fever, unexplained weight loss, and potentially neurological symptoms like weakness and tingling. Risk factors primarily involve living in or visiting endemic regions, particularly the Mississippi, Ohio, and St. Lawrence River valleys, as well as the Great Lakes area. Exposure to soil containing the Blastomyces fungus increases the risk. The infection often starts in the lungs but can disseminate to other organs, including the bones, skin, and brain, making early diagnosis crucial.

3

Why is Blastomycosis often misdiagnosed, and what are the consequences of such misdiagnosis?

Blastomycosis is often misdiagnosed because its symptoms, such as cough and fever, can mimic those of other respiratory illnesses, including Tuberculosis (TB). This similarity in symptoms makes it challenging to differentiate between the two without specific diagnostic tests. A misdiagnosis of Blastomycosis as TB can lead to inappropriate treatment, as the standard TB treatment is ineffective against the fungal infection. The consequences include a lack of improvement in the patient's condition, potential disease progression, and the spread of the infection to other organs, leading to severe complications.

4

What diagnostic steps are crucial in identifying Blastomycosis, especially when TB treatment fails?

When initial treatment for TB fails, further diagnostic testing is essential. This may include a chest X-ray or CT scan to assess lung involvement, and an MRI to evaluate potential spread to the brain or other organs. The presence of lesions in the lungs or brain should raise suspicion. Specific diagnostic tests, such as broncho-alveolar lavage (BAL) to identify Blastomyces spp., and other fungal cultures and tests are critical for confirmation. The case highlights that when symptoms persist despite initial treatment, considering less common infections like Blastomycosis and pursuing further diagnostic testing is critical.

5

How is Blastomycosis treated, and what is the prognosis for patients?

The primary treatment for Blastomycosis involves antifungal medications. Intravenous liposomal Amphotericin B is often used initially for severe cases, followed by oral Itraconazole. The prognosis for patients with Blastomycosis is generally good, especially with early diagnosis and appropriate treatment. In the case presented, the patient's symptoms resolved after two months of antifungal treatment, and follow-up imaging showed significant improvement. However, the outcome depends on the severity of the infection, the extent of spread, and how quickly the correct diagnosis and treatment are implemented. Continued monitoring and follow-up are crucial to ensure complete recovery and prevent recurrence.

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