Uncommon Disseminated Fungal Infections¶

Chapter 226 | Part 5: Infectious Diseases · Part 5 – Infectious Diseases: Fungal · Chapter 226

Key Clinical Points¶

Paracoccidioidomycosis: Pathognomonic 'mariner's wheel' yeast morphology (multiple daughter cells attached circumferentially via narrow-necked buds).
Talaromycosis: Characterized by bipolar fission (two elliptical yeasts separated by a central septation) and ~10% mortality with treatment.
Fusariosis: Identified by acute angle septate hyphae and banana-shaped macroconidia; mortality approaches 100% if neutropenia persists.
Phaeohyphomycosis: Defined by melanized, golden-brown hyphae on H&E; Voriconazole is preferred for CNS involvement.
Scedosporiosis/Lomentosporiosis: Lomentospora prolificans is resistant to almost all commercially available antifungal drugs.
Emergomycosis: Diagnosis relies on histopathologic identification of adiaspores with surrounding granulomas.
Clinical Presentation: Talaromycosis mimics disseminated histoplasmosis; Fusariosis often presents with painful necrotic skin lesions in neutropenic patients.
Diagnostic Clues: Blood cultures are positive in 50% of disseminated fusariosis cases; T. marneffei produces red pigment in culture.
Treatment Strategy: Amphotericin B is the initial choice for severe/systemic cases, followed by transition to oral agents (Itraconazole/Posaconazole).
Risk Factors: Neutropenia and advanced AIDS are primary drivers for opportunistic infections like Talaromycosis and Fusariosis.

1. DEFINITION & OVERVIEW¶

• Phaeohyphomycosis:

Definition: Infections caused by melanin-producing fungi with filamentous growth. ◦ Includes eumycetoma, chromoblastomycosis, and invasive infections from dematiaceous molds. ◦ Melanin acts as a virulence factor, enabling these organisms to evade immune detection. ◦ Most infections are localized but can disseminate in immunocompromised hosts. ◦ Key pathogens: Fusarium, Scedosporium, and Lomentospora.

1.1 Sporotrichosis Treatment Context¶

• Lymphocutaneous sporotrichosis: Continue therapy for 2–4 weeks after lesion resolution (total duration 3–6 months). Success rate ~90–100%. • Pulmonary/osteoarticular forms: Itraconazole for ≥1 year. • Severe disease/CNS involvement: Initiate with amphotericin B, switch to itraconazole after improvement. • AIDS patients: Lifelong suppressive itraconazole often required.

2. EPIDEMIOLOGY¶

• Eumycetoma: Predominantly in Sudan, Mexico, India; 50% of mycetomas are fungal. • Chromoblastomycosis: Latin America, Madagascar, China; Cladophialophora carrionii thrives in semiarid climates. • Paracoccidioidomycosis: Highest incidence in Brazil/Colombia/Venezuela/Ecuador; 14:1 male-to-female ratio. • Talaromycosis: Linked to bamboo rats; rare in immunocompetent hosts; common in advanced AIDS. • Emergomycosis: Reported globally (Europe, Asia, Africa, Americas); E. pasteurianus most widespread. • Adiaspiromycosis: Occupational soil exposure risk; self-limiting but can cause respiratory failure.

2.1 Risk Factors¶

• Inoculation: Minor trauma with soil/plant material. • Immune Deficits: ◦ Inborn errors of immunity (IL-12/IFN-γ pathway) → increased paracoccidioidomycosis risk. ◦ Neutropenia → critical for fusariosis susceptibility. ◦ Chronic granulomatous disease (CGD) → increased fusariosis risk (less than aspergillosis).

3. ETIOLOGY & PATHOPHYSIOLOGY¶

• Dematiaceous Fungi: Contain melanin, causing dark pigmentation. • Paracoccidioides brasiliensis: Thermally dimorphic; endemic to Central/South America. • Talaromyces marneffei: Dimorphs (formerly Penicillium); prevalent in Southeast Asia. • Emergomyces species: Form adiaspores that trigger granulomatous inflammation. • Fusarium species: Produce banana-shaped macroconidia; neutrophils are key for host defense. • Scedosporium/Lomentospora: Major opportunistic pathogens.

3.1 Dimorphic Fungi Pathogenesis¶

• Morphology Shift: Convert between mold (environmental) and yeast (infection) at 35°C. ◦ Examples: Paracoccidioides, Talaromyces marneffei, Emergomyces species.

3.2 Host Defense Mechanisms¶

• Talaromycosis: Controlled by neutrophils and IFN-γ-primed macrophages. • Phaeohyphomycosis: Dectin-1/CARD9 pathway mediates proinflammatory cytokine production. ◦ ~70% of immunocompetent patients with disseminated phaeohyphomycosis have CLEC7A variants.

4. CLINICAL FEATURES¶

• Eumycetoma (Madura foot): Chronic lower extremity infection with sinus tracts and fungal grains. • Chromoblastomycosis: Slow-growing nodular lesions on lower limbs. • Paracoccidioidomycosis: ◦ Acute form: <30yo, reticuloendothelial dissemination, peripheral eosinophilia. ◦ Chronic form: >90% of cases, older men, pulmonary fibrosis and mucocutaneous ulcers. • Talaromycosis: ◦ Mimics disseminated histoplasmosis (fever, weight loss, lymphadenopathy, hepatosplenomegaly). ◦ Skin lesions: Umbilicated papules resembling molluscum contagiosum. • Fusariosis: ◦ Angioinvasive in immunocompromised patients. ◦ Common presentations: Keratitis and CNS abscesses. ◦ Skin: Nodular or necrotic painful lesions (often shortly after/concurrent with fever).

4.1 Paracoccidioidomycosis Syndromes¶

• Acute: <30yo, reticuloendothelial dissemination, peripheral eosinophilia. • Chronic: ~90% of cases, older men, lower lobe pulmonary fibrosis, mucocutaneous ulcers.

4.2 Talaromycosis Clinical Presentation¶

• Systemic: Fever, weight loss, lymphadenopathy, hepatosplenomegaly. • Cutaneous: Umbilicated papules (resemble molluscum contagiosum). • Organ Involvement: Liver/bone marrow common; CNS involvement rare.

5. DIFFERENTIAL DIAGNOSIS¶

• Paracoccidioidomycosis: Distinguish from leishmaniasis and squamous cell carcinoma. ◦ Note: Adrenal insufficiency may occur with adrenal gland involvement. • Talaromycosis: Mimics disseminated histoplasmosis. • Fusariosis: Differentiate from aspergillosis (similar CT findings). • Scedosporiorsis: Similar to aspergillosis in pulmonary presentation.

6. INVESTIGATIONS & DIAGNOSIS¶

Clinical Presentation & Imaging: ◦ Identify characteristic signs (e.g., sinus tracts for mycetoma, umbilicated papules for Talaromycosis).
Histopathology (Primary Diagnostic Tool): ◦ Paracoccidioidomycosis → identify 'mariner's wheel' yeast with narrow-necked buds. ◦ Talaromycosis → identify bipolar fission yeasts (two elliptical cells with central septation). ◦ Phaeohyphomycosis → identify golden-brown melanized hyphae on H&E; confirm with Fontana-Masson stain. ◦ Emergomycosis → identify adiaspores with surrounding granulomas.
Culture & Molecular Methods: ◦ Talaromycosis → Blood/biopsy cultures (T. marneffei produces red pigment). ◦ Chromoblastomycosis → PCR for 28S rRNA/ITS if culture-negative. ◦ Fusariosis → Blood cultures (positive in 50% of disseminated cases); identify banana-shaped macroconidia on agar.
Specific Diagnostic Clues: ◦ Paracoccidioidomycosis: Mariner's wheel morphology. ◦ Talaromycosis: Bipolar fission yeast morphology. ◦ Phaeohyphomycosis: Golden-brown melanized hyphae on H&E. ◦ Fusariosis: Blood culture positivity and banana-shaped macroconidia.

7. MANAGEMENT & TREATMENT¶

Paracoccidioidomycosis: ◦ Chronic form: Itraconazole 100–200 mg/day for 6–12 months. ◦ Acute (juvenile) form: Lipid AmB until improvement → Itraconazole 200 mg twice daily for 12 months. ◦ Mild or moderate: Itraconazole 200 mg twice daily for 12 weeks; Voriconazole or posaconazole as alternatives. ◦ Maintenance (AIDS): Itraconazole 200 mg/day until CD4+ >100/μL for ≥6 months.
Talaromycosis: ◦ Systemic: Amphotericin B (0.7–1.0 mg/kg/day) + itraconazole (200–400 mg/day). ◦ CNS involvement: Voriconazole (200–300 mg BID).
Fusariosis: ◦ Initial: Amphotericin B. ◦ Follow-up: Itraconazole or posaconazole. ◦ CNS involvement: Voriconazole.
Scedosporiosis & Lomentosporiosis: ◦ First-line: Voriconazole 200–300 mg twice daily; Posaconazole 300 mg/day. ◦ Note: Not susceptible to AmB; Lomentospora prolificans is resistant to almost all commercially available drugs (consider olorofim or fosmanogepix if available).
Phaeohyphomycosis: ◦ Options: Voriconazole 200–300 mg twice daily; Itraconazole 200 mg twice daily; Posaconazole 300 mg/day. ◦ Note: Lipid AmB may be effective against some mold species.

Treatment Summary Table (Table 226-1)¶

• Paracoccidioidomycosis: ◦ Chronic: Itraconazole 100–200 mg/day for 6–12 months. ◦ Acute: Lipid AmB until improvement → Itraconazole 200 mg twice daily for 12 months. ◦ Mild/Moderate: Itraconazole 200 mg twice daily for 12 weeks; Voriconazole or Posaconazole alternatives. • Phaeohyphomycosis: ◦ Voriconazole 200–300 mg twice daily; Itraconazole 200 mg twice daily; Posaconazole 300 mg/day. ◦ Lipid AmB (5 mg/kg/day) for some species. • Scedosporiosis & Lomentosporiosis: ◦ Voriconazole 200–300 mg twice daily; Posaconazole 300 mg/day. ◦ Note: Lomentospora prolificans is resistant to almost all available drugs.

8. PROGNOSIS & COMPLICATIONS¶

• Paracoccidioidomycosis: ◦ Chronic form: Good prognosis with antifungal therapy. ◦ Acute form: Can be fatal without treatment. • Talaromycosis: ◦ Mortality ≈ 10% with treatment. • Fusariosis: ◦ High mortality (50–90%) in immunocompromised patients; mortality approaches 100% if neutropenia persists. • Phaeohyphomycosis: ◦ Poor prognosis in disseminated disease; CNS involvement increases risk. • Emergomycosis: ◦ Self-limiting but can cause respiratory failure.

Mortality Rates¶

• Talaromycosis: ≈ 10% with treatment. • Fusariosis: 50–90% in immunocompromised; ≈ 100% if neutropenia persists. • Phaeohyphomycosis: High mortality in disseminated disease.

9. SPECIAL CONSIDERATIONS¶

• Immunocompromised States: ◦ AIDS, neutropenia, and transplant recipients increase risk for disseminated infections. ◦ Voriconazole is preferred for CNS involvement. ◦ Amphotericin B may be ineffective against some dematiaceous molds but used in specific cases. • Specific Conditions: ◦ Neutropenia → increased fusariosis risk/mortality. ◦ Transplant recipients → high risk for scedosporiorsis/fusariosis. ◦ Lomentospora prolificans: Highly drug-resistant; consider olorofim or fosmanogepix.

10. KEY PEARLS & CLINICAL TRAPS¶

• Phaeohyphomycosis: Melanin stains (Fontana-Masson) are critical for diagnosis. • Fusariosis: Blood cultures positive in 50% of disseminated cases; look for banana-shaped macroconidia. • Talaromycosis: Bipolar fission yeast morphology is diagnostic. • Paracoccidioidomycosis: Mariner's wheel yeast (narrow-necked buds) is pathognomonic. • Scedosporiorsis: Lomentospora prolificans is highly drug-resistant.

Reference Tables¶

TABLE 226-1 Suggested Treatment for Uncommon Disseminated Fungal Infections DISEASE Paracoccidioidomycosis Chronic…¶

Harrison's 22e, p.1726

DISEASE	FIRST-LINE THERAPY	ALTERNATIVES/COMMENTS
Paracoccidioidomycosis
	Itraconazolea, 100–200 mg/day for 6–12 months
Acute (juvenile form)	Lipid AmBb until improvement	Itraconazolea, 200 mg twice daily after AmB for 12 months Voriconazole or posaconazole at doses noted above may be used
Mild or moderate	Itraconazolea, 200 mg twice daily for 12 weeks	Voriconazolea, 200 mg twice daily Posaconazolea 300 mg/day
	Lipid AmBb until improvement
Maintenance therapy (AIDS)	Itraconazole, 200 mg/day until CD4+ T cell count is >100/μL for ≥6 months
Mild or moderate	Itraconazolea 200 mg twice daily for 12 weeks	Voriconazolea, 200 mg twice daily Posaconazolea 300 mg/day
	Lipid AmBb until improvement
Phaeohyphomycosis	Voriconazolea, 200 mg twice daily Itraconazolea, 200 mg twice daily Posaconazolea, 300 mg/day	Lipid AmB may be effective against some mold species
	Voriconazolea, 200–300 mg twice daily Lipid AmB, 5 mg/kg/day Posaconazolea, 300 mg/day
Scedosporiosis and lomentosporiosis	Voriconazolea, 200–300 mg twice daily Posaconazolea, 300 mg/day	Not susceptible to AmB. Lomentospora prolificans is resistant to almost all commercially available antifungal drugs. Investigational olorofim or fosmanogepix may be considered if available.
	Voriconazolea, 200–300 mg twice daily