Systemic Mycoses with Cutaneous Manifestations

Systemic Mycoses with Cutaneous Manifestations

Systemic Mycoses with Cutaneous Manifestations

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Systemic Mycoses: Intro - Deep Skin Invaders

  • Systemic mycoses: Fungal infections originating deep within the body, capable of disseminating to skin and other organs.
  • Routes: Inhalation (primary lung focus), direct inoculation.
  • Host status: Crucial. Immunocompromised (↑risk, severity); Immunocompetent (endemic, often self-limiting).
  • Key Types:
    • Dimorphic fungi (e.g., Histoplasma, Coccidioides)
    • Opportunistic: Yeasts (e.g., Cryptococcus), Moulds (e.g., Aspergillus) Skin biopsy for fungal infection diagnosis

⭐ Most systemic mycoses are acquired via inhalation of spores, leading to a primary pulmonary infection before cutaneous dissemination.

Dimorphic Mycoses - Two-Faced Terrors

Dimorphic fungi: molds in environment, yeasts in tissue ($37^\circ C$).

FungusEndemic Areas (📌 Mnemonic)RouteKey Systemic FeaturesCharacteristic Cutaneous LesionsDiagnosis (Tissue Form)
Histoplasma capsulatumOhio-Mississippi River valleys (US), Ganga-Brahmaputra plains (India) (📌 Histo in Caves/Rivers)InhalationPneumonia, hepatosplenomegaly (disseminated)Papules, nodules, ulcers (disseminated)Small intracellular yeasts
Blastomyces dermatitidisN. America (Ohio, Mississippi River valleys), parts of IndiaInhalationPneumonia, bone lesions, GU involvementVerrucous, crusted, ulcerative (mimics SCC/TB)Broad-based budding yeasts
Coccidioides immitis/posadasiiSW USA, Mexico, C/S America (📌 Coco in the Valley Fever)InhalationFlu-like illness, pneumonia, meningitisErythema nodosum/multiforme (reactive); papules, pustules, verrucous (disseminated)Spherules with endospores
Paracoccidioides brasiliensisCentral/South America (esp. Brazil)InhalationLungs, lymph nodes, oral/nasal mucosaMulberry-like ulcers (oral/nasal), verrucous"Mariner's wheel" yeasts

Paracoccidioides brasiliensis yeast cells show a characteristic 'Mariner's wheel' appearance in tissue an important diagnostic clue often tested in exams.

Opportunistic Mycoses - Vulnerable Targets

  • Cryptococcosis:
    • Species: C. neoformans (AIDS), C. gattii
    • Predisposing: HIV (CD4 < 100 cells/µL), steroids, transplant
    • Skin: Umbilicated papules/nodules (molluscum-like), cellulitis, ulcers.
    • Dx: India ink (CSF), Cryptococcal antigen (CrAg) (serum/CSF)
  • Systemic Candidiasis:
    • Species: C. albicans, C. tropicalis
    • Predisposing: Neutropenia, central lines, TPN, broad-spectrum antibiotics
    • Skin: Diffuse erythematous macronodules (often tender), pustules
  • Invasive Aspergillosis:
    • Species: A. fumigatus, A. flavus
    • Predisposing: Prolonged neutropenia, high-dose steroids, Chronic Granulomatous Disease (CGD)
    • Skin:
      • Primary (direct inoculation): Necrotic plaques/pustules at trauma/IV sites
      • Secondary (hematogenous): Ecthyma gangrenosum-like lesions, hemorrhagic bullae
  • Mucormycosis:
    • Genera: Rhizopus, Mucor, Lichtheimia
    • Predisposing: Diabetic Ketoacidosis (DKA), neutropenia, iron overload (e.g., deferoxamine therapy), burns
    • Skin: Necrotic black eschars; Rhino-orbito-cerebral (ROC) form can extend to facial skin.

⭐ Cutaneous cryptococcosis can be the first sign of disseminated disease in AIDS patients, often when CD4 count is very low.

Diagnosis & Management - Attack Plan

  • Polyenes (Amphotericin B): Binds ergosterol, forms pores. Broadest spectrum. Major toxicity: Nephrotoxicity.
  • Azoles (Fluconazole, Itraconazole, Voriconazole, Posaconazole): Inhibit ergosterol synthesis. Key for many mycoses. Major toxicities: Hepatotoxicity, drug interactions.

    ⭐ Voriconazole is the drug of choice for invasive aspergillosis.

  • Echinocandins (Caspofungin, Micafungin): Inhibit β-(1,3)-D-glucan synthesis. For Candida, Aspergillus. Generally well-tolerated.
  • Flucytosine: Converted to 5-FU, inhibits DNA/RNA synthesis. Combination therapy (e.g., cryptococcosis). Major toxicity: Myelosuppression.

High‑Yield Points - ⚡ Biggest Takeaways

  • Systemic mycoses: Caused by dimorphic fungi, common in immunocompromised patients.
  • Histoplasmosis: Features oral ulcers, reticuloendothelial involvement; critical in AIDS.
  • Blastomycosis: Shows verrucous skin lesions, lung disease; broad-based budding yeast on microscopy.
  • Coccidioidomycosis: Presents with erythema nodosum/multiforme; spherules with endospores are diagnostic.
  • Paracoccidioidomycosis: Key signs are mucocutaneous lesions and "mariner's wheel" yeast.
  • Sporotrichosis: Known for lymphocutaneous spread ("rose gardener's disease"); cigar-shaped yeast.
  • Cryptococcosis: May cause molluscum-like skin lesions; India ink shows capsulated yeast.

Practice Questions: Systemic Mycoses with Cutaneous Manifestations

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Which of the following is NOT a fungal infection?

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Flashcards: Systemic Mycoses with Cutaneous Manifestations

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_____ is a subcutaneous mycotic infection, usually caused by traumatic inoculation which presents with verrucous lesions

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_____ is a subcutaneous mycotic infection, usually caused by traumatic inoculation which presents with verrucous lesions

Chromoblastomycosis (chromomycosis)

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