SUBCUTANEOUS MYCOSES

• Subcutaneous mycoses


  Dermatophytes that cause subcutaneous mycoses are normal saprophytic inhabitants of soil and decaying vegetation
• Subcutaneous mycoses


  • They must be introduced into the body beneath the cutaneous layer
  • Examples include chromoblastomycosis, maduromycosis, and sporotrichosis
• Most infections involve barefooted agricultural workers
• Development of subcutaneous mycoses

  1. Nodule formation

  2. Ulceration

  3. Spread along lymphatic channels producing more subcutaneous nodules

  4. Nodules drain to skin surface
• Treatment for subcutaneous mycoses

  Administration of oral 5-fluorocytosine, iodides, amphotericin B, and surgical excision
• Diagnosis of subcutaneous mycoses

  Culture of infected tissue
• Sporotrichosis

  Subcutaneous mycosis caused by the thermally dimorphic fungus Sporothrix schenckii
• Sporotrichosis


  • Occurs worldwide
  • Fungus can be found in soil, on living plants, or in plant debris
  • Infection occurs through a puncture wound contaminated with the fungus
  • Occupational hazard for florists, gardeners, and forestry workers
• Progression of sporotrichosis

  1. Small red papule arises and begins to ulcerate

  2. New lesions appear along lymph channels, can remain localized or spread throughout the body
• Sporotrichosis diagnosis


  Aspiration fluid, pus, or biopsy samples examined microscopically, cultured, and tested serologically
• Direct microscopic examination of exudate has little diagnostic value as demonstrating the characteristic yeast forms is difficult
• Sporothrix schenckii


  • Mycelial phase: small moist white colonies becoming leathery
  • Hyphae: branching with bouquet-like clusters of conidia
  • Yeast phase: pasty and greenish, spherical to oval with cigar-shaped "asteroid" cells
• Sporothrix schenckii colonies grow rapidly (3-5 days) and can be mistaken for yeast initially
• Sporothrix schenckii microscopic features

  • Narrow, septate, branching hyphae
  • Two types of conidia: slender tapering conidiophores and thick-walled brown to black sessile conidia
• Sporothrix schenckii yeast phase

  Round to ovoid cells of varying size, producing single or multiple buds often resembling "rabbit ears" or "Mickey Mouse ears"
• Sporotrichosis treatment


  • Cutaneous infection: potassium iodide (topical/oral)
  • Disseminated infection: amphotericin B
• Chromoblastomycosis


  Subcutaneous mycosis with pigmented dark brown nodules, caused by black molds Phialophora verrucosa or Fonsecaea pedrosoi
• Chromoblastomycosis


  • Posttraumatic chronic infection of subcutaneous tissue
  • Papules become verrucous cauliflower-like lesions, usually on lower extremities
  • Systemic invasion is very rare
• Chromoblastomycosis causative agents


  • Fonsecaea
  • Phialophora
  • Cladophialophora
• Chromoblastomycosis diagnosis

  • Direct examination of 10% KOH cleared lesion scrapings shows muriform (sclerotic) cells
  • Culture on Sabouraud dextrose agar shows slow-growing, dark, velvety colonies
• Biopsy of chromoblastomycosis shows hyperkeratosis, central neutrophilic abscesses and granulomas, and variable pigmented fungal structures
• Dextrose Agar


  Culture medium for slow-growing, dark, velvety colonies with a black obverse seen on culture of the infectious agents
• Dextrose Agar culture


  • Incubated for 4-6 weeks at 37°C
• Chromoblastomycosis


  Subcutaneous mycosis caused by dematiaceous fungi
• Diagnosis of Chromoblastomycosis


  1. Fonsecaea: mixed sporulation (Acrotheca, Cladosporium, Phialophora)

  2. Phialophora: only phialophora sporulation

  3. Cladosporium: only cladosporium sporulation
• Biopsy


  Diagnostic procedure for Chromoblastomycosis
• Subcutaneous mycoses


  Dermatophytes that cause them are normal saprophytic inhabitants of soil and decaying vegetation
• Biopsy specimen analysis


  1. Stained with H&E, Giemsa Stain and Fontana-Masson Stain

  2. Shows hyperkeratosis, central neutrophilic abscesses and granulomas

  3. May show variable pigmented fungal structures like muriform cells (Medlar bodies)
• Subcutaneous mycoses


  • Require a puncture wound that has been contaminated with soil containing the fungi to penetrate the skin
  • Must be introduced into the body beneath the cutaneous layer
• Muriform cells


  Aggregation of dark brown cells (diameter: 4-10 um), rounded, brown, and have fission planes, resemble "COPPER PENNIES"
• Subcutaneous mycoses


  • chromoblastomycosis
  • maduromycosis
  • sporotrichosis
• Most infections involve barefooted agricultural workers
• Chromoblastomycosis


  • Spreads very slowly, rarely fatal, usually has a good prognosis, but can be very difficult to cure
• Treatment options for Chromoblastomycosis

  • Oral & locally applied itraconazole
  • Heat therapy
  • Cryosurgery
  • Laser therapy
  • Surgery
• Development of subcutaneous mycoses

  1. Fungi produce a nodule that eventually ulcerates

  2. Organisms spread along lymphatic channels producing more subcutaneous nodules

  3. Nodules may drain to the skin surface
• Surgical excision of an early solitary lesion is preferred for Chromoblastomycosis
• Treatments for subcutaneous mycoses

  • Oral 5-fluorocytosine
  • Iodides
  • Amphotericin B
  • Surgical excision
• Diagnosis of subcutaneous mycoses

  Culture of the infected tissue
• Mycetoma


  Subcutaneous mycosis caused by Madurella mycetomatis, also known as Maduromycosis or Madura foot
• Types of subcutaneous mycoses

  • Sporotrichosis
  • Chromoblastomycosis
  • Mycetoma
  • Rhinosporidiosis
  • Lobomycosis