What are the classifications and treatments of subcutaneous fungal infections?

Classification and Treatment of Subcutaneous Fungal Infections

Subcutaneous fungal infections are classified into five main categories: sporotrichosis, chromoblastomycosis, phaeohyphomycosis, eumycotic mycetoma, and hyalohyphomycosis, each requiring specific antifungal therapy and often surgical intervention for optimal management.

Main Classifications of Subcutaneous Fungal Infections

Subcutaneous mycoses represent a heterogeneous group of fungal infections that develop after traumatic inoculation of fungi into the dermis and subcutaneous tissues 1, 2. These infections typically remain localized but can spread to adjacent tissues and lymphatics, with rare hematogenous dissemination 2.

The five major categories include:

1. Sporotrichosis

   • Most common in temperate regions
   • Caused by Sporothrix species
   • Presents as nodular lymphangitic spread from inoculation site
   • Often mistaken for bacterial infection 3

2. Chromoblastomycosis

   • Characterized by verrucous, warty lesions
   • Caused by dematiaceous (pigmented) fungi
   • Common in tropical and subtropical regions

3. Phaeohyphomycosis

   • Caused by dematiaceous fungi
   • Presents as cystic or nodular lesions

4. Eumycotic Mycetoma

   • Characterized by the triad of tumefaction, draining sinuses, and grain formation
   • Multiple fungal species can cause this condition

5. Hyalohyphomycosis

   • Caused by non-pigmented fungi
   • Various clinical presentations

Diagnosis

Early and accurate diagnosis is crucial for proper management:

• Clinical presentation: Varies by specific infection but often includes nodules, abscesses, or verrucous lesions at the site of trauma 4
• Histopathology: Essential for identifying fungal elements in tissue
• Culture: Gold standard for species identification 5
• Molecular biology: Increasingly used for accurate diagnosis when culture is negative or inconclusive 5

Treatment Approaches

Treatment should be tailored to the specific fungal pathogen:

Sporotrichosis

• First-line: Oral itraconazole (200-400 mg daily) for 3-6 months
• Alternative: Potassium iodide solution for lymphocutaneous forms
• Severe cases: Amphotericin B for disseminated disease

Chromoblastomycosis

• Antifungal therapy: Itraconazole (200-400 mg daily) or terbinafine (250-500 mg daily) for months to years
• Adjunctive treatments: Surgical excision for small lesions, cryotherapy, or local heat therapy
• Refractory cases: Combination therapy with itraconazole and terbinafine

Mycetoma

• Eumycotic (fungal): Long-term itraconazole or voriconazole combined with surgical debridement
• Treatment duration: Often 12+ months
• Surgical intervention: Critical for extensive disease

Phaeohyphomycosis

• Localized infection: Surgical excision with wide margins
• Systemic therapy: Itraconazole, voriconazole, or posaconazole
• Severe cases: Amphotericin B formulations

Hyalohyphomycosis

• Treatment based on specific pathogen
• Fusarium infections: High-dose IV voriconazole or posaconazole 6

Special Considerations for Immunocompromised Patients

Immunocompromised patients require more aggressive evaluation and treatment:

• Blood cultures should be obtained, and skin lesions should be aggressively evaluated by culture aspiration, biopsy, or surgical excision 6
• Empiric antifungal therapy may be necessary in neutropenic patients with persistent fever 6
• Surgical debridement is crucial for cultures and sensitivities and to remove devitalized tissue 6

Specific Fungal Pathogens in Immunocompromised Hosts

1. Candida species

   • Superficial cutaneous candidiasis presents as intertrigo, vaginitis, balanitis, perleche, and paronychia 6
   • Invasive disseminated candidiasis may present with pink to red papules on trunk and extremities 6

2. Trichosporon beigelii

   • Uncommon but frequently fatal disseminated fungal infection 6
   • Presents with multiple erythematous macules to maculopapular lesions 6

3. Aspergillus species

   • Occurs in 10-14% of patients with profound and prolonged neutropenia 6
   • Cutaneous infections may occur at IV catheter sites or nail beds 6
   • Treatment: Voriconazole 6

4. Rhizopus and Mucor species

   • Angioinvasive molds causing painful erythematous nodules that become necrotic 6
   • Require aggressive surgical debridement and antifungal therapy 6

5. Fusarium species

   • Common in patients with prolonged neutropenia 6
   • Present with multiple erythematous macules with central pallor that evolve to necrotic nodules 6
   • Treatment: High-dose IV voriconazole or posaconazole 6

Prevention and Management Pitfalls

Common Pitfalls

• Delayed diagnosis of necrotizing infections
• Inadequate use of broad-spectrum antibiotics
• Failure to reevaluate treatment response within 24-48 hours 7

Prevention Strategies

• Controlling comorbidities such as diabetes
• Practicing good hygiene
• Early mobilization and exercise to promote recovery 7

Conclusion

Early recognition, proper diagnosis through culture and histopathology, and appropriate antifungal therapy are essential for successful management of subcutaneous fungal infections. Surgical intervention often plays a critical role, particularly in extensive or refractory disease. Immunocompromised patients require more aggressive evaluation and treatment approaches to prevent dissemination and reduce mortality.