Subcutaneous Mycoses

Intro: SubQ Mycoses - Sneaky Skin Fungi

• Fungal infections affecting dermis, subcutaneous tissues, often extending to muscle/fascia.
• Characterized by slow, chronic progression; generally localized, rarely disseminate.
• Caused by fungi commonly residing in soil or on vegetation (saprophytes).
• Mode of entry: Traumatic implantation of fungal spores/hyphae into skin.

⭐ Subcutaneous mycoses are typically acquired through traumatic implantation of fungal elements into the skin, often from soil or vegetation.

Sporotrichosis - Rose Gardener's Peril

• Organism: Sporothrix schenckii (dimorphic: mold in cold, yeast in heat).
• Transmission: Traumatic inoculation from soil/plants (e.g., rose thorns 📌 "Rose Gardener's Disease").
• Clinical (Lymphocutaneous type - most common):
  • Initial lesion: painless papule/nodule at inoculation site, may ulcerate.
  • Follows lymphatic drainage: linear chain of subcutaneous nodules ("sporotrichoid spread").
• Diagnosis:
  • Culture (Sabouraud Dextrose Agar, SDA): thermal dimorphism (yeast at 37°C, mycelial/mold at 25°C).
  • Biopsy/Microscopy: Cigar-shaped budding yeasts; Asteroid bodies (Splendore-Hoeppli phenomenon - Ag-Ab complexes).
• Treatment: Itraconazole (Drug of Choice). Saturated Solution of Potassium Iodide (SSKI) for fixed cutaneous. Amphotericin B for severe/disseminated cases.

⭐ Sporothrix schenckii typically causes a lymphocutaneous infection, with nodules appearing along lymphatic channels.

Mnemonic: "Sporothrix schenckii typically causes a lymphocutaneous infection, with nodules appearing along lymphatic channels."

Chromoblastomycosis - Copper Penny Culprits

• Etiology: Dematiaceous (pigmented) fungi; Fonsecaea pedrosoi (most common), Phialophora verrucosa, Cladophialophora carrionii.
• Transmission: Traumatic inoculation of fungal elements from soil/vegetation.
• Clinical: Chronic, slowly progressive. Verrucous, warty, cauliflower-like nodules/plaques. "Black dots" (hemorrhagic points) on surface. Usually on lower limbs.
• Diagnosis:
  • Microscopy (KOH/biopsy): Pathognomonic Medlar bodies (sclerotic cells, muriform cells, 'copper pennies') - thick-walled, pigmented, septate cells.

⭐ The presence of Medlar bodies (sclerotic cells, 'copper pennies') in tissue biopsy is diagnostic for Chromoblastomycosis.

• Treatment: Itraconazole, terbinafine; surgery, cryotherapy, local heat. Often refractory to treatment.

Mycetoma - Grainy Discharge Drama

• Chronic granulomatous infection: skin, subcutaneous tissue, fascia, bone.
• 📌 Triad: Tumefaction (swelling), Draining Sinuses, Granules (grains).
• Grains: Visible colonies; color aids diagnosis.

• Eumycetoma: Larger grains; poorer medical response, often needs surgery.
• Actinomycetoma: Smaller grains; better response to prolonged antibiotics.

⭐ Mycetoma is characterized by the clinical triad of tumefaction, draining sinuses, and the presence of granules (grains).

Other Mycoses - SubQ Rarities

• Phaeohyphomycosis
  • Etiology: Dematiaceous (pigmented) fungi (e.g., Exophiala, Wangiella).
  • Clinical: Solitary cysts, nodules, plaques; disseminated in immunocompromised.
  • Diagnosis: Pigmented (brown) septate hyphae in tissue.
• Lobomycosis (Lobo's Disease)
  • Etiology: Lacazia loboi.
  • Clinical: Chronic keloidal, verrucous skin lesions (ears, limbs).
  • Diagnosis: Chains of yeast-like cells ("string of beads"). Amazon basin endemic.
• Rhinosporidiosis
  • Etiology: Rhinosporidium seeberi (aquatic protist).
  • Clinical: Polypoidal, friable, vascular "strawberry-like" nasal/ocular masses.
  • Diagnosis: Large, thick-walled sporangia with numerous endospores.

  ⭐ Rhinosporidiosis, caused by Rhinosporidium seeberi, typically presents as friable, polypoidal masses in the nose and nasopharynx containing large sporangia with endospores.

High‑Yield Points - ⚡ Biggest Takeaways

• Sporotrichosis: "Rose gardener's disease", lymphocutaneous spread, cigar-shaped yeasts, asteroid bodies.
• Chromoblastomycosis: Sclerotic bodies (copper pennies), warty lesions, caused by dematiaceous fungi.
• Mycetoma: Granules in discharge, tumefaction, draining sinuses; distinguish eumycetoma (fungal) from actinomycetoma.
• Phaeohyphomycosis: Caused by dematiaceous fungi with pigmented hyphae in tissue.
• Rhinosporidiosis: Nasal/ocular polyps with large sporangia and endospores.
• Diagnosis: Direct microscopy (KOH, biopsy) and culture are crucial.
• Treatment: Often itraconazole; surgery may be needed_._