What are the contrast‑enhanced CT thorax findings in invasive Trichosporon infection?

CECT Thorax Findings in Invasive Trichosporon Infection

Invasive Trichosporon infection on CECT thorax typically presents with nodular or cavitary lesions similar to other invasive filamentous fungal infections, though specific imaging patterns for Trichosporon are not well-characterized in the literature and must be distinguished from Aspergillus and other molds through microbiological confirmation.

Primary CT Findings

The available evidence does not provide Trichosporon-specific CT imaging patterns. However, as Trichosporon is classified among emerging filamentous fungi 1, the CT findings likely mirror those of invasive mold infections:

Expected Patterns (Based on Invasive Fungal Disease Guidelines)

• Nodular lesions - Most common finding in invasive filamentous fungal infections 2
• Cavitary lesions - Suggestive of invasive fungal infection 2
• Consolidation - May be present, particularly in neutropenic patients 2
• Halo sign - Ground-glass opacity surrounding nodules, indicating hemorrhagic infarction in early invasive mold infection 2
• Air-crescent sign - Later finding suggesting treatment response 2

Key Distinguishing Features

Recent multicenter research demonstrates that invasive Aspergillus and non-Aspergillus infections (which would include Trichosporon) show 3:

• 93% prevalence of nodules (significantly higher than Pneumocystis)
• 58% ground-glass opacities (significantly lower than Pneumocystis at 96%)
• 5% lymphadenopathy (significantly lower than Pneumocystis at 41%)

Clinical Context Critical for Interpretation

High-Risk Populations

Trichosporon infections occur predominantly in:

• Solid organ transplant recipients (especially lung transplant) 4, 5
• Severely immunocompromised patients 1, 6
• Patients on breakthrough antifungal therapy (particularly echinocandins) 4, 6

Infection Patterns

• Surgical site origin in 87.5% of transplant cases 4
• Progression to fungemia associated with 100% mortality in one series 4
• Pleural involvement with empyema formation 7

Critical Diagnostic Pitfalls

The most important caveat: CT findings alone cannot distinguish Trichosporon from other invasive fungal infections 2. The differential diagnosis for nodular/cavitary lesions includes:

• Aspergillus species
• Zygomycetes/Mucorales
• Fusarium species
• Nocardia
• Mycobacteria
• Pseudomonas aeruginosa
• Malignancy

Mandatory Next Steps

When CT shows findings suggestive of invasive fungal infection:

1. Do not delay antifungal therapy while pursuing diagnosis 2
2. Obtain microbiological confirmation via:
   • Blood cultures (positive in fungemic cases)
   • Bronchoalveolar lavage with culture
   • Molecular diagnostics (pan-fungal rDNA sequencing, mNGS) - crucial for Trichosporon identification 7, 6
3. Compare to prior CT scans in the individual patient 2

Follow-up Imaging Considerations

• Do not repeat CT within 7 days of treatment initiation 2
• Increasing infiltrate volume in the first week does not indicate treatment failure 2
• Development of air-crescent sign or reduction of halo sign indicates favorable response 2

Prognostic CT Features

In invasive non-Aspergillus mold infections:

• Nodules with halo sign associated with adverse outcome (42.5% in poor outcome vs 15.9% in favorable outcome, p<0.0001) 3
• Consolidations more common in neutropenic patients (66%) versus transplant recipients (27%) 3