Uncommon Disseminated Fungal Infections¶
Chapter 226 | Part 12: Endocrinology
KEY CLINICAL POINTS¶
- Eumycetoma and chromoblastomycosis are caused by dematiaceous fungi (brown-black molds) and are endemic in tropical/subtropical regions.
- Paracoccidioidomycosis is caused by Paracoccidioides species, with a strong male predominance and chronic pulmonary involvement.
- Talaromycosis (Emergomyces) is a thermally dimorphic fungus linked to immunocompromised hosts, with treatment requiring amphotericin B and triazoles.
- Phaeohyphomycoses are infections by pigmented molds, often disseminated in immunocompromised patients, requiring prolonged antifungal therapy.
- Fusariosis, scedosporiosis, and lomentosporiosis are aggressive infections in immunocompromised hosts, often resistant to conventional antifungals.
1. DEFINITION & OVERVIEW¶
Uncommon disseminated fungal infections include eumycetoma, chromoblastomycosis, paracoccidioidomycosis, talaromycosis, and phaeohyphomycoses. These infections are caused by thermally dimorphic or dematiaceous fungi, often affecting immunocompromised individuals. Dissemination occurs via hematogenous spread, leading to systemic involvement of organs.
Table 226-1 Suggested Treatment for Uncommon Disseminated Fungal Infections¶
| DISEASE | FIRST-LINE THERAPY | ALTERNATIVES/COMMENTS |
|---|---|---|
| Paracoccidioidomycosis (Chronic) | Itraconazole 100–200 mg/day for 6–12 months | Voriconazole 200 mg twice daily, Posaconazole 300 mg/day |
| Paracoccidioidomycosis (Acute) | Lipid AmB until improvement | Itraconazole 200 mg twice daily after AmB for 12 months |
| Talaromycosis | Itraconazole 200 mg twice daily for 12 weeks | Lipid AmB until improvement |
| Phaeohyphomycosis | Voriconazole 200 mg twice daily | Itraconazole 200 mg twice daily, Posaconazole 300 mg/day |
| Fusariosis | Lipid AmB + voriconazole/posaconazole | Fosmanogepix or olorofim (investigational) |
| Scedosporiosis/Lomentosporiosis | Voriconazole 200–300 mg twice daily | Posaconazole 300 mg/day; AmB not effective |
1.1 Eumycetoma and Chromoblastomycosis¶
Eumycetoma (Madura foot) is a chronic subcutaneous infection with granulomas and fungal grains. Chromoblastomycosis is a verrucous cutaneous infection with muriform cells. Both are caused by dematiaceous fungi (e.g., Madurella, Fonsecaea).
1.2 Paracoccidioidomycosis¶
A dimorphic fungal infection caused by Paracoccidioides species, primarily affecting immunocompromised individuals. Chronic pulmonary involvement is common, with dissemination to CNS and other organs.
1.3 Talaromycosis (Emergomyces)¶
A thermally dimorphic fungus (Talaromyces marneffei) causing disseminated infection in immunocompromised hosts, particularly in Southeast Asia. Characterized by systemic granulomas and neutrophilic inflammation.
2. EPIDEMIOLOGY¶
Eumycetoma and chromoblastomycosis are endemic in tropical/subtropical regions (e.g., Sudan, Mexico, India). Paracoccidioidomycosis is prevalent in Central/South America, with Brazil, Colombia, and Venezuela as high-incidence areas. Talaromycosis is common in Southeast Asia, particularly in immunocompromised patients. Adiaspiromycosis is linked to occupational exposure to soil and dust.
2.1 Risk Factors¶
Immunocompromised states (AIDS, corticosteroids, organ transplantation), trauma, and environmental exposure to soil/plants. Male predominance in paracoccidioidomycosis (14:1–70:1 ratio).
2.2 Demographics¶
Eumycetoma and chromoblastomycosis affect rural adult males. Paracoccidioidomycosis is most common in middle-aged/elderly men. Talaromycosis is prevalent in Southeast Asia among immunocompromised hosts.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Dematiaceous fungi (e.g., Madurella, Fonsecaea) cause eumycetoma/chromoblastomycosis via traumatic inoculation. Paracoccidioides species are thermally dimorphic, transitioning to yeast in host tissues. Talaromyces marneffei is a dimorphic fungus causing systemic infection. Phaeohyphomycoses are caused by pigmented molds (e.g., Cladophialophora, Exophiala) that form muriform cells. Fusarium, Scedosporium, and Lomentospora are hyaline molds causing invasive infections.
3.1 Dimorphic Fungi¶
Paracoccidioides and Talaromyces are thermally dimorphic, switching to yeast forms at body temperature. This allows systemic dissemination in immunocompromised hosts.
3.2 Melanin Production¶
Melanin in dematiaceous fungi contributes to virulence by resisting phagocytosis and oxidative stress. Muriform cells (thick-walled, multiseptated) are diagnostic for chromoblastomycosis.
4. CLINICAL FEATURES¶
Eumycetoma presents with subcutaneous granulomas, sinus tracts, and fungal grains. Chromoblastomycosis has verrucous skin lesions. Paracoccidioidomycosis causes chronic pulmonary disease with granulomas. Talaromycosis presents with systemic granulomas and neutrophilic inflammation. Phaeohyphomycoses manifest as disseminated infections with pigmented hyphae.
4.1 Paracoccidioidomycosis¶
Chronic pulmonary disease with granulomas, fibrosis, and mucocutaneous lesions. Acute form presents with disseminated reticuloendothelial infection in children.
4.2 Talaromycosis¶
Systemic granulomas in lungs, liver, bone marrow, and CNS. Pulmonary lesions may mimic histoplasmosis, with cross-reactivity in serologic tests.
5. DIFFERENTIAL DIAGNOSIS¶
Eumycetoma vs. actinomycosis; chromoblastomycosis vs. leishmaniasis/squamous cell carcinoma; paracoccidioidomycosis vs. histoplasmosis/blastomycosis; talaromycosis vs. histoplasmosis. Phaeohyphomycoses must be differentiated from aspergillosis/mucormycosis.
5.1 Key Differentiators¶
Muriform cells in chromoblastomycosis vs. yeast forms in histoplasmosis. Paracoccidioides' mariner’s wheel morphology vs. Histoplasma. Talaromyces' neutrophilic granulomas vs. other fungal infections.
6. INVESTIGATIONS & DIAGNOSIS¶
Culture of fungal organisms from blood/tissue, histopathology showing muriform cells or pigmented hyphae, and PCR for specific fungal DNA. Serologic tests (e.g., antigen detection) may have cross-reactivity. Imaging (CT) for pulmonary involvement.
6.1 Diagnostic Criteria¶
Culture confirmation of dematiaceous fungi, histopathologic evidence of muriform cells, and imaging for systemic spread. PCR for rapid identification of specific pathogens.
6.2 Laboratory Tests¶
Blood cultures for Scedosporium/Lomentospora, fungal antigen tests (e.g., Histoplasma), and susceptibility testing for antifungal agents.
7. MANAGEMENT & TREATMENT¶
Surgical debridement and antifungal therapy are required. Itraconazole is first-line for most infections, with voriconazole/posaconazole as alternatives. Amphotericin B is used for severe cases. Long-term suppressive therapy is needed for immunocompromised patients.
7.1 Antifungal Therapy¶
Itraconazole (200 mg/day), voriconazole (200 mg twice daily), or posaconazole (300 mg/day) for most infections. Amphotericin B for severe cases until improvement, followed by triazole therapy.
7.2 Special Populations¶
AIDS patients require lifelong suppressive itraconazole. Corticosteroid use increases risk of talaromycosis. Neutropenic patients need prompt antifungal therapy.
8. PROGNOSIS & COMPLICATIONS¶
Eumycetoma/chromoblastomycosis have high cure rates with surgery and antifungals. Paracoccidioidomycosis responds well to therapy, but pulmonary fibrosis may occur. Talaromycosis has ~10% mortality with treatment. Fusariosis/scedosporiosis have high mortality (up to 85%) due to resistance and dissemination.
8.1 Complications¶
Fractures, bacterial superinfection, CNS involvement, adrenal insufficiency, and granulomatous inflammation. Disseminated infections are often fatal without prompt treatment.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: Avoid amphotericin B due to teratogenic risk. Pediatrics: Monitor for drug toxicity. Elderly: Consider renal function for antifungal dosing. Immunocompromised patients require prolonged suppressive therapy.
9.1 AIDS Patients¶
Lifelong itraconazole suppressive therapy required. Monitor CD4+ counts to discontinue prophylaxis.
10. KEY POINTS & CLINICAL PEARLS¶
- Eumycetoma and chromoblastomycosis are caused by dematiaceous fungi; surgical excision is critical. 2. Paracoccidioidomycosis is a dimorphic fungus with a strong male predominance. 3. Talaromycosis requires amphotericin B and triazoles. 4. Phaeohyphomycoses need prolonged antifungal therapy. 5. Fusariosis/scedosporiosis are resistant to conventional antifungals and have high mortality.