Blastomycosis: Symptoms, Types, Causes and Treatment

Blastomycosis is a fascinating yet serious fungal infection that often gets overlooked because it can mimic more common respiratory illnesses. Caused by environmental fungi in the genus Blastomyces, this disease can affect anyone—healthy or immunocompromised, young or old—especially those living in or traveling through certain geographic hotspots. Understanding the symptoms, types, causes, and treatment options for blastomycosis is crucial for timely diagnosis and effective care. This article provides a comprehensive, evidence-based overview of blastomycosis, tailored to help patients, caregivers, and healthcare professionals recognize and manage this complex infection.

Symptoms of Blastomycosis

Recognizing the symptoms of blastomycosis can be challenging, as they are often non-specific and easily mistaken for other respiratory diseases. However, certain features—especially when combined with exposure history—can raise suspicion and prompt further investigation.

Symptom	Frequency/Feature	Distinguishing Clues	Source(s)
Cough	Common (13.1%), often persistent	Less frequent than in other fungal diseases	2 4
Fever	Infrequent (2.6%)	Less common than in pneumonia/influenza	2 4
Chest pain	Pleuritic, present in both acute and chronic	Can occur without effusion	2 3
Skin lesions	Seen in disseminated or chronic forms	Nodules/ulcers, may be mistaken for cancer	3 6 8
Night sweats	Common, especially in pulmonary disease		2
Weight loss	Common, especially with chronic infection		2 3
Pulmonary nodules	Sometimes solitary, sometimes multiple	Suggests fungal etiology	4
Bone/joint pain	Seen in disseminated disease	Involvement of long bones/joints	3 6 8
Hemoptysis	Rare, but possible in severe pulmonary cases	May indicate severe infection	5

Table 1: Key Symptoms

Acute vs. Chronic Symptoms

Blastomycosis can present acutely or chronically:

• Acute form: Develops over days to weeks, often with toxic symptoms—such as fever, chills, pleuritic chest pain, and rapid onset of pneumonia. Chest X-rays may show consolidations but typically no effusions. The course can be relatively benign or severe, sometimes progressing to adult respiratory distress syndrome (ARDS) if not treated promptly 3 5 6.
• Chronic form: Symptoms develop over months to years, with a more indolent course. Patients may experience cough, weight loss, night sweats, and low-grade fevers. Chronic cases have a higher risk of dissemination to the skin, bones, and other organs 2 3 6.

Distinguishing Symptoms from Other Diseases

Blastomycosis can closely mimic bacterial pneumonia, tuberculosis, or even cancer, making diagnosis tricky. Unlike classic pneumonia or flu, fever is less common in blastomycosis, and certain features—such as solitary nodules, lymph node enlargement, or skin lesions—are more suggestive of a fungal origin 4.

Extrapulmonary Manifestations

• Cutaneous: Wart-like, ulcerative, or nodular lesions often appear in disseminated disease. These may be mistaken for skin cancers or other infections.
• Osteoarticular: Joint and bone pain, with possible involvement of long bones or the spine.
• Rare symptoms: Hemoptysis (coughing blood), particularly in immunocompromised individuals or severe cases; hepatosplenomegaly (enlarged liver/spleen) in chronic disseminated forms 3 5 8.

Types of Blastomycosis

Blastomycosis is not a single disease but encompasses a spectrum of clinical presentations and is caused by several related fungal species. Understanding these types helps guide diagnosis, management, and prognosis.

Type	Description	Common Sites	Source(s)
Pulmonary	Most common, ranges from mild to severe pneumonia	Lungs	2 3 6
Disseminated	Spread beyond lungs—skin, bones, CNS, others	Skin, bone, CNS, GU	3 6 7 8
Acute	Rapid onset, toxic symptoms	Lungs (mainly)	3 6
Chronic	Months/years, slow progression, risk of spread	Lungs, extrapulmonary	3 6 8
Species-variant	Caused by different Blastomyces species	Varies by geography	6 7 8 9

Table 2: Types of Blastomycosis

Pulmonary Blastomycosis

• Primary and most common form.
• Typically presents as pneumonia, with symptoms like cough, chest pain, and breathlessness.
• Can be self-limited or progress to severe disease.
• In immunosuppressed patients or if unrecognized, can lead to ARDS and death 2 3 5 6.

Disseminated Blastomycosis

• Occurs when the fungus spreads hematogenously from the lungs to other organs.
• Most often affects the skin (ulcers, nodules), bones/joints (pain, swelling), and genitourinary tract; rarely, the central nervous system 3 6 7 8.
• More frequent in chronic cases and in immunocompromised individuals.

Acute vs. Chronic Forms

• Acute blastomycosis: Sudden onset, rapid progression, and more severe systemic symptoms.
• Chronic blastomycosis: Slow progression, with a higher risk of misdiagnosis (e.g., as tuberculosis or cancer), and greater likelihood of disseminated disease 3.

Blastomycosis by Species

• Blastomyces dermatitidis and Blastomyces gilchristii: Most common in North America 1 6.
• Blastomyces helicus: Found in western North America, can cause atypical disease 6 9.
• Blastomyces percursus and Blastomyces emzantsi: Predominant in Africa and the Middle East, associated with cutaneous and osteoarticular disease 7 8 9.
• Disease presentation can vary depending on the species involved and geographic region.

Causes of Blastomycosis

Blastomycosis is primarily an environmentally acquired infection. Understanding its causes provides insight into who is at risk and how the disease can be prevented.

Cause/Factor	Mechanism or Risk	Notable Details	Source(s)
Blastomyces spp.	Inhalation of spores from soil/decaying matter	Dimorphic fungi, mold-to-yeast shift	1 6 9
Environmental	Proximity to waterways, moist soil	High risk near rivers/lakes	2 6
Immunosuppression	Reduced immune defense	More severe/fatal disease	1 5 6
Geographic region	Endemic in North America, Africa, Middle East	Species distribution varies	6 7 8 9

Table 3: Causes and Risk Factors

The Fungus: Blastomyces spp.

• Thermally dimorphic fungi: Exist as mold in the environment; switch to yeast form in human tissue.
• Species of concern:
  • B. dermatitidis and B. gilchristii (North America)
  • B. helicus (western North America)
  • B. percursus and B. emzantsi (Africa, Middle East) 6 7 8 9

Modes of Transmission

• Inhalation of spores: Infection occurs after breathing in conidia (spores) from disturbed soil, decaying wood, or organic debris.
• No person-to-person transmission: The disease is not contagious between individuals 1 6.

Environmental and Geographic Factors

• High-risk areas: Regions near waterways, rivers, lakes, and moist soils—especially in the midwestern and eastern United States, as well as parts of Africa and the Middle East 2 6 8.
• Seasonal occurrence: More cases reported during cooler months (December–April) in endemic areas 2.

Host Factors

• Immunosuppression: Individuals with weakened immune systems (due to illness or medications) have a higher risk of severe, rapidly progressive, or disseminated disease 1 5 6.
• Otherwise healthy individuals: Most cases occur in immunocompetent people who live near or visit endemic areas 2 6.

Treatment of Blastomycosis

Effective treatment of blastomycosis relies on prompt diagnosis and appropriate antifungal therapy, tailored to the severity and site of infection, immune status, and the specific Blastomyces species involved.

Therapy/Approach	Indication	Notes/Drugs Used	Source(s)
Amphotericin B	Severe, CNS, immunosuppressed, pregnancy	First-line for life-threatening disease	1 5 6 11 14
Itraconazole	Mild-moderate, non-CNS, step-down therapy	Preferred oral agent	6 11 12 14
Fluconazole	Alternative for non-life-threatening cases	Moderate efficacy, longer duration	13 14
Voriconazole/Posaconazole	Azole-intolerant or special cases	Second-line options	6 7
Monitoring/follow-up	All patients	Assess for relapse, drug side effects	11 12 14

Table 4: Treatment Approaches

General Principles

• Most patients require therapy: Spontaneous cure may occur in some immunocompetent individuals with mild, acute pulmonary disease, but close monitoring is essential 14.
• Treatment is mandatory: For all immunocompromised patients, those with progressive or extrapulmonary disease, CNS involvement, or severe pulmonary illness 6 11 14.

Choice of Antifungal Therapy

Amphotericin B

• Indications: Severe disease, CNS involvement, immunosuppression, pregnancy.
• Formulations: Lipid formulations are preferred due to better safety profiles.
• Considerations: IV administration, potential for kidney toxicity 1 5 6 11 14.

Itraconazole

• Indications: Mild-to-moderate pulmonary or extrapulmonary disease (excluding CNS).
• Dosing: Oral, with serum levels monitored to ensure efficacy (combined itraconazole and hydroxy-itraconazole >1.0 mcg/mL recommended) 12.
• Preferred agent: Due to higher efficacy and lower toxicity compared to ketoconazole or fluconazole 6 11 12 14.

Fluconazole

• Indications: Alternative for non-life-threatening, non-CNS disease.
• Efficacy: Moderately effective, especially in cases where other azoles are not tolerated; requires prolonged therapy (at least 6 months) 13 14.
• Limitations: Not first-line due to lower efficacy.

Other Azoles (Voriconazole, Posaconazole)

• Indications: Used when patients cannot tolerate itraconazole or in cases of resistant species.
• Evidence: In vitro activity shown, especially for African species 6 7.

Monitoring and Duration

• Treatment duration: Usually several months (6–12 months), depending on severity and site.
• Monitoring: Regular follow-up to assess clinical response, adverse drug reactions, and serum drug levels.
• Relapse: Watch for relapse or disease progression, particularly in immunocompromised hosts 11 12.

Special Considerations

• Pregnancy: Amphotericin B is the only approved drug.
• CNS disease: Requires aggressive therapy with amphotericin B and possibly extended azole therapy 6 11 14.
• Immunosuppressed patients: Require more intensive therapy and monitoring due to higher risk of severe outcomes 1 5 6 11.

Conclusion

Blastomycosis is a complex infection with a wide range of clinical presentations, caused by several related fungal species and influenced by geographic, environmental, and host factors. Prompt recognition and appropriate treatment are essential for preventing severe complications and improving outcomes.

Key Points:

• Symptoms: Often non-specific and mimic other diseases; persistent cough, chest pain, weight loss, and skin or bone lesions in chronic/disseminated forms are clues 2 3 4 6 8.
• Types: Acute and chronic pulmonary forms are most common; disseminated disease affects skin, bones, and other organs, with species and geography influencing presentation 3 6 7 8 9.
• Causes: Environmental dimorphic fungi acquired by inhalation; risk higher near waterways and in endemic regions; immunosuppression increases severity 1 2 6 7 8 9.
• Treatment: Antifungal therapy tailored to severity, site, and host status; amphotericin B for severe disease, itraconazole for mild to moderate cases, with alternatives as needed 6 11 12 13 14.

Early suspicion, especially in patients from endemic areas who do not improve with standard pneumonia treatments, is vital for saving lives and reducing morbidity.