What are the main American mycoses?

Main American Mycoses

The primary endemic mycoses in the Americas are histoplasmosis, blastomycosis, coccidioidomycosis, paracoccidioidomycosis, and sporotrichosis, with histoplasmosis being the most prevalent in North America. 1

North American Endemic Mycoses

The three major endemic mycoses in North America that clinicians must recognize are:

Histoplasmosis

• Most prevalent endemic mycosis in North America, occurring predominantly in the Mississippi and Ohio River valleys, midwestern states, and Canadian provinces bordering the Great Lakes 1, 2
• Caused by Histoplasma capsulatum, a dimorphic fungus found in soil enriched with bird or bat droppings 1, 3
• Mortality rates: 5% in children and 8% in adults 1
• Clinical presentations range from asymptomatic infection to disseminated disease, with pulmonary involvement being most common 1

Blastomycosis

• Endemic to southeastern and south central states bordering the Mississippi and Ohio Rivers, midwestern states and Canadian provinces near the Great Lakes, and areas adjacent to the St. Lawrence River 1, 2
• Caused by Blastomyces dermatitidis, acquired through inhalation of conidia from moist soil with decaying vegetation 1, 2
• Presents as acute or chronic pneumonia, with extrapulmonary dissemination to skin, bone, genitourinary tract, and rarely CNS 1
• Asymptomatic infection occurs in at least 50% of exposed individuals 1

Coccidioidomycosis

• Restricted to semiarid regions of the southwestern United States and contiguous areas of Mexico, with limited endemic foci in Central and South America 2, 4
• Caused by Coccidioides immitis, with arthroconidia present in soil of endemic areas 2
• Handling cultures represents a serious laboratory biohazard 2
• Racial predisposition to disseminated disease exists, though the mechanism remains unclear 2

Latin American Endemic Mycoses

Paracoccidioidomycosis

• Caused by Paracoccidioides species, representing a major endemic mycosis in Latin America 1
• Included among the seven most commonly encountered endemic mycoses requiring clinical management 1

Sporotrichosis

• Caused by Sporothrix species, recognized as a significant endemic mycosis in the Americas 1
• Part of the global burden of endemic mycoses that continues to rise yearly 1

Clinical Significance

All these endemic mycoses are leading causes of patient morbidity and mortality worldwide, requiring thorough understanding of epidemiology, risk factors, and diagnostic approaches. 1

Key Clinical Considerations:

• Each fungus occupies a specific ecological niche and can cause disease in both healthy and immunocompromised hosts 1
• These dimorphic fungi are classified within Ascomycota and share phylogenetic relationships that influence antifungal susceptibility patterns 3
• Amphotericin B is FDA-approved for treating potentially life-threatening infections including aspergillosis, cryptococcosis, North American blastomycosis, systemic candidiasis, coccidioidomycosis, histoplasmosis, and sporotrichosis 5
• In immunocompromised patients (particularly those with HIV), widespread dissemination from pulmonary foci occurs frequently, requiring amphotericin B as initial therapy followed by azole maintenance 6

Diagnostic Pitfalls:

• Cross-reactivity between endemic mycoses is problematic—Histoplasma antigen is detected in the majority of patients with blastomycosis, coccidioidomycosis, paracoccidioidomycosis, and talaromycosis 1
• Limited commercial availability of antigen testing, especially outside the United States, delays diagnosis in severe infections 1
• Culture remains the gold standard but is time-consuming; rapid diagnosis through antigen and antibody testing is essential for severe infections 1