Blastomycosis in Children
Introduction to Blastomycosis in Children
Blastomycosis is a systemic fungal infection caused by Blastomyces dermatitidis and Blastomyces gilchristii. While it can affect individuals of all ages, blastomycosis in children presents unique challenges in diagnosis and management.
Key points:
- Blastomycosis is endemic in certain regions of North America, particularly around the Great Lakes and Mississippi River valley.
- The infection can range from asymptomatic to severe, potentially life-threatening disease.
- Pediatric blastomycosis can affect multiple organ systems, with pulmonary involvement being most common.
- Early recognition and appropriate treatment are crucial for preventing complications and improving outcomes.
Epidemiology of Blastomycosis in Children
Understanding the epidemiology of blastomycosis in children is important for recognition and management:
- Geographic distribution:
- Endemic in parts of North America, especially the Ohio and Mississippi River valleys and the Great Lakes region
- Sporadic cases reported in other parts of the world
- Incidence:
- Overall incidence is low, estimated at 1-2 cases per 100,000 in endemic areas
- Pediatric cases account for about 2-13% of all reported cases
- Risk factors:
- Living in or traveling to endemic areas
- Outdoor activities, especially in wooded areas
- Excavation or construction work (more relevant for adolescents)
- Immunocompromised status (e.g., HIV infection, organ transplantation)
- Age and gender distribution:
- Can affect children of all ages, but more common in older children and adolescents
- Slight male predominance observed in some studies
Pathogenesis of Blastomycosis
The pathogenesis of blastomycosis involves complex interactions between the fungus and host:
- Infection acquisition:
- Inhalation of fungal spores (conidia) from soil or organic matter
- Direct inoculation through skin (rare)
- Fungal factors:
- Thermally dimorphic fungus: mold at 25°C, yeast at 37°C
- Conversion to yeast form is crucial for pathogenicity
- Cell wall components (e.g., α-1,3-glucan) contribute to virulence
- Host response:
- Innate immune response: Phagocytosis by alveolar macrophages and neutrophils
- Adaptive immunity: T-cell-mediated response is critical for control
- Granulomatous inflammation is a hallmark of the infection
- Dissemination:
- Hematogenous spread from lungs to other organs (e.g., skin, bones, CNS)
- Lymphatic spread can also occur
Clinical Presentation of Blastomycosis in Children
Blastomycosis can present with a wide range of clinical manifestations in children:
- Pulmonary blastomycosis:
- Acute: Flu-like illness with fever, cough, and chest pain
- Chronic: Productive cough, weight loss, chest pain, hemoptysis
- Can mimic bacterial pneumonia or tuberculosis
- Disseminated blastomycosis:
- Cutaneous lesions: Verrucous or ulcerative skin lesions
- Bone involvement: Osteomyelitis, typically in long bones or vertebrae
- Central nervous system: Meningitis, brain abscess (rare in children)
- Genitourinary system: Prostatitis, epididymitis (in adolescent males)
- Acute respiratory distress syndrome (ARDS):
- Severe, rapidly progressive pneumonia
- More common in immunocompromised children
- Asymptomatic infection:
- Incidentally discovered on chest imaging
- May represent early or self-limited infection
Diagnosis of Blastomycosis in Children
Accurate diagnosis of blastomycosis is crucial for appropriate management:
- Clinical suspicion:
- Based on symptoms and epidemiological factors
- Consider in cases of pneumonia unresponsive to antibiotics in endemic areas
- Microscopy and culture:
- Direct microscopy of clinical specimens (sputum, tissue, pus)
- Culture on Sabouraud's dextrose agar (gold standard, but slow growth)
- Histopathology:
- Characteristic broad-based budding yeasts in tissue samples
- Special stains: Grocott's methenamine silver (GMS), Periodic acid-Schiff (PAS)
- Antigen detection:
- Urine Blastomyces antigen test (cross-reactivity with other fungi)
- Serum antigen testing also available
- Molecular methods:
- PCR-based assays for rapid detection (not widely available)
- Imaging studies:
- Chest X-ray: Focal or diffuse infiltrates, mass-like lesions
- CT scan: More detailed assessment of pulmonary involvement
- Bone scans or MRI for suspected osseous involvement
Treatment of Blastomycosis in Children
Treatment approaches depend on the severity and extent of the infection:
- Mild to moderate pulmonary or disseminated disease:
- Itraconazole: 10 mg/kg/day (max 400 mg/day) for 6-12 months
- Severe pulmonary disease or CNS involvement:
- Amphotericin B (lipid formulation): 3-5 mg/kg/day for 1-2 weeks
- Followed by itraconazole for a total of 12 months
- Life-threatening disease or ARDS:
- Amphotericin B (lipid formulation): 5 mg/kg/day
- Consider adjunctive corticosteroids in severe ARDS
- Immunocompromised patients:
- Longer duration of therapy may be necessary
- Close monitoring for relapse
- Supportive care:
- Management of respiratory complications
- Nutritional support
Prevention of Blastomycosis in Children
While complete prevention is challenging, certain measures can reduce the risk:
- Environmental awareness:
- Educate families about endemic areas and high-risk activities
- Avoid disturbing soil in heavily wooded areas
- Personal protective measures:
- Use of dust masks during high-risk activities (e.g., excavation, gardening)
- Proper wound care to prevent cutaneous inoculation
- High-risk groups:
- Consider prophylaxis for severely immunocompromised children in endemic areas (not routinely recommended)
- Early recognition:
- Prompt evaluation of persistent respiratory symptoms in endemic areas
- Increased awareness among healthcare providers
- Public health measures:
- Reporting of cases to local health authorities
- Environmental testing and control in outbreak settings
Blastomycosis in Children
- What is the causative agent of blastomycosis?
Blastomyces dermatitidis, a dimorphic fungus - Which geographic regions are most commonly associated with blastomycosis infections?
North America, particularly the Mississippi and Ohio River valleys, and the Great Lakes region - What is the primary mode of transmission for blastomycosis in children?
Inhalation of fungal spores from contaminated soil or organic matter - What age group of children is most commonly affected by blastomycosis?
School-aged children and adolescents - What are the most common symptoms of pulmonary blastomycosis in children?
Fever, cough, chest pain, and shortness of breath - How long is the typical incubation period for blastomycosis?
3 to 15 weeks, with an average of 45 days - What diagnostic test is considered the gold standard for confirming blastomycosis?
Culture and microscopic identification of Blastomyces dermatitidis from clinical specimens - Which organ system, other than the lungs, is most commonly affected in disseminated blastomycosis?
The skin - What is the characteristic appearance of skin lesions in cutaneous blastomycosis?
Verrucous or ulcerative lesions with irregular borders - What is the first-line treatment for mild to moderate blastomycosis in children?
Oral itraconazole - In severe cases of blastomycosis, what is the initial treatment of choice?
Intravenous amphotericin B - What is the typical duration of treatment for blastomycosis in children?
6 to 12 months, depending on disease severity and clinical response - What complication can occur in children with untreated pulmonary blastomycosis?
Acute respiratory distress syndrome (ARDS) - Which immunocompromised children are at higher risk for developing severe or disseminated blastomycosis?
Children with HIV/AIDS, organ transplant recipients, and those on long-term corticosteroid therapy - What is the mortality rate for children with treated blastomycosis?
Less than 5% with appropriate treatment - Can blastomycosis be transmitted from person to person?
No, it is not contagious between individuals - What is the most common radiographic finding in pulmonary blastomycosis?
Focal pneumonia or mass-like infiltrates - What serological test can be used to aid in the diagnosis of blastomycosis?
Blastomyces antigen detection in urine or serum - What is the name of the yeast form of Blastomyces dermatitidis observed in tissue samples?
Broad-based budding yeast - Which outdoor activities increase the risk of exposure to Blastomyces dermatitidis in endemic areas?
Exploring caves, camping, and activities involving disruption of soil or decaying vegetation - What is the term for the reactivation of latent blastomycosis infection?
Endogenous reinfection - Can blastomycosis affect the central nervous system in children?
Yes, it can cause meningitis or brain abscesses in severe cases - What is the recommended follow-up for children treated for blastomycosis?
Regular clinical and radiographic evaluations for at least one year after treatment completion - What is the most common misdiagnosis for pulmonary blastomycosis in children?
Community-acquired pneumonia - Can pregnant adolescents with blastomycosis transmit the infection to their fetus?
Yes, transplacental transmission is possible but rare - What is the role of corticosteroids in the management of blastomycosis in children?
They may be used in severe cases with ARDS, but should be administered with antifungal therapy - What is the significance of eosinophilia in children with blastomycosis?
It can be a helpful diagnostic clue, as eosinophilia is present in up to 30% of cases - Can blastomycosis cause osteomyelitis in children?
Yes, bone involvement occurs in approximately 25% of disseminated cases - What is the primary mechanism of action for azole antifungals used in treating blastomycosis?
Inhibition of ergosterol synthesis in the fungal cell membrane - What is the recommended approach for treating blastomycosis in children with HIV/AIDS?
Longer duration of therapy and lifelong suppressive treatment may be necessary
