Subcutaneous Mycoses

Introduction - Deep Skin Invaders

• Fungi invade dermis, subcutaneous tissue, muscle, fascia.
• Chronic, localized infections.
• Caused by diverse, saprophytic fungi.
• Portal of entry: Skin trauma (thorns, splinters).
• Organisms reside in soil, decaying vegetation.
• Infections often indolent, slowly progressive.
• Host immunity plays a key role in disease manifestation.

⭐ Subcutaneous mycoses typically result from traumatic inoculation of fungi from soil or vegetation into deeper skin layers.

• Common in tropical/subtropical regions, agricultural workers.
• Diagnosis: Microscopy, culture, histopathology, molecular tests (PCR).

Sporotrichosis - Rose Gardener's Revenge

• Agent: Sporothrix schenckii (thermally dimorphic fungus).
• Transmission: Traumatic inoculation from soil, sphagnum moss, rose thorns.
• Clinical Forms:
  • Lymphocutaneous (most common): Initial papule → ulcerates. Nodules ascend along lymphatics ("sporotrichoid spread").
  • Fixed cutaneous: Solitary chronic plaque/ulcer.
  • Disseminated: Rare; in immunocompromised (joints, lungs).
• Diagnosis:
  • Culture (gold standard): Tissue/pus. Yeast at 37°C, mold at 25°C.
  • Biopsy: Granulomatous inflammation; cigar-shaped yeast cells.

  ⭐ The presence of asteroid bodies (Splendore-Hoeppli phenomenon) surrounding yeast cells is characteristic but not pathognomonic for sporotrichosis.

• Treatment:
  • Itraconazole (DOC for cutaneous/lymphocutaneous).
  • SSKI (Saturated Solution of Potassium Iodide).
  • Amphotericin B (severe/disseminated).

Chromo & Phaeo - Dark Fungi Drama

• Caused by dematiaceous (dark-walled/pigmented) fungi.
• Chromoblastomycosis:
  • Etiology: Fonsecaea pedrosoi, Phialophora verrucosa, Cladophialophora carrionii.
  • Clinical: Chronic, progressive; verrucous, crusted, warty, “cauliflower-like” plaques/nodules. Often on lower limbs.
  • Diagnosis: Histopathology shows pathognomonic sclerotic bodies (Medlar bodies, “copper pennies”).
  • Treatment: Itraconazole, terbinafine, local heat therapy, surgery.
• Phaeohyphomycosis:
  • Etiology: Heterogeneous group of pigmented fungi (e.g., Exophiala, Wangiella, Bipolaris).
  • Clinical: Highly variable; subcutaneous cysts/abscesses, sinusitis, keratitis, brain abscess (especially in immunocompromised).
  • Diagnosis: Pigmented (brown/black) septate hyphae, yeast-like cells, or pseudohyphae in tissue; NO sclerotic bodies.
  • Treatment: Surgical excision + antifungals (e.g., itraconazole, voriconazole, amphotericin B).

⭐ Sclerotic bodies (Medlar bodies or 'copper pennies') are pathognomonic for chromoblastomycosis and represent fungal cells undergoing cell division by fission.

Mycetoma - Grainy Swellings Saga

• Chronic granulomatous infection: skin, subcutaneous tissue. Often foot (Madura foot), hand.
• Triad: Painless swelling, multiple sinuses, discharge of grains.
• Types & Grains:
  • Eumycetoma (fungal): Madurella mycetomatis (black grains). Slower progression.
  • Actinomycetoma (bacterial): Nocardia, Actinomadura (white/yellow/red grains). Faster progression. 📌 "Actino Ants March with Sulfa Drugs" (Actinomycetoma treated with antibiotics like sulfonamides).

⭐ The color of grains discharged from sinuses in mycetoma (e.g., black, white, yellow, red) can provide a clue to the causative organism (eumycetoma vs. actinomycetoma).

• Dx: Clinical, grain microscopy (KOH, Gram), culture, imaging (X-ray, USG, MRI - "dot-in-circle" sign).
• Rx:
  • Eumycetoma: Antifungals (e.g., itraconazole) + surgical debridement.
  • Actinomycetoma: Antibiotics (e.g., Welsh regimen: TMP-SMX + Dapsone/Amikacin).

High‑Yield Points - ⚡ Biggest Takeaways

• Sporotrichosis: "Rose gardener's disease", lymphocutaneous spread along lymphatics; Sporothrix schenckii.
• Mycetoma: Triad: tumefaction, draining sinuses, grains/granules; Madurella mycetomatis (eumycetoma, black grains).
• Chromoblastomycosis: Verrucous/warty lesions, pathognomonic sclerotic bodies (Medlar bodies/copper pennies).
• Rhinosporidiosis: Nasal/ocular friable polyps; R. seeberi showing large sporangia with endospores.
• Typically from traumatic inoculation of soil fungi; diagnosis by microscopy (KOH, biopsy) & culture.
• Treatment: Prolonged systemic antifungals (e.g., Itraconazole) often combined with surgical debridement.