Updated: 2/25/2019

Cutaneous and Subcutaneous Mycoses

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Snapshot
  • A veterinarian presents to his primary care physician for a growing pustule on his right forearm. He reports that he often embarks on hikes through fields and forests, bringing back injured animals to treat. He denies any known animal bites or scratches but recalls being pricked by a thorn while hiking. He denies any fevers, chills, nausea, vomiting, conjunctivitis, or sore throat. On physical exam, there is a 0.5 cm pustule with surrounding erythema and multiple scattered nodules along his right forearm. He is prescribed an oral agent for this disease. (Sporotrichosis)
Introduction
  • Introduction
    • cutaneous mycoses
      • tinea (dermatophytes)
        • tinea capitis
        • tinea corporis
        • tinea cruris
        • tinea pedis
        • tinea unguium
      • tinea versicolor (pityriasis)
    • subcutaneous mycoses
      • sporothrix schenkii
Tinea (Dermatophytes)
  • Introduction
    • organisms are dermatophytes
      • Microsporum spp.
      • Trichophyton spp.
      • Epidermophyton spp.
    • demographics
      • most common fungal infection in the pediatric population
      • common in children
    • transmission
      • direct contact
  • Presentation
    • pruritus
Tinea (Dermatophytes)
  Tinea capitis
Tinea corporis ("ringworm")
Tinea cruris ("jock itch")
Tinea pedis ("athlete's foot")
Tinea unguium (onychomycosis)
Location
  • Head
  • Scalp
  • Torso
  • Inguinal
  • Feet
  • Nails
Clinical characteristics
  • Lymphadenopathy
  • Itchy and scaly plaques with associated alopecia
  • Erythematous annular lesions with central clearing and scaly border
  • Well-demarcated erythematous scaly rash, often symmetric without central clearing
  • Interdigital feet infection
  • Plantar erythema (moccasin distribution)
  • Vesicles, bullae, or pustules
  • Nail thickening
  • Nail discoloration
  • No pain or itching
Risk factors
  • African American or Carribbean descent
  • Contact with infected pet
  • Adolescent and adult males
  • Physical activities that cause sweating
  • Occlusive footwear
  • Warm and moist environment
  • Occlusive footwear
  • Warm and moist environment
  • Immunosuppression
  • Communal bathing
Treatment
  • Oral antifungals (topicals will not penetrate hair follicles)
  • Topical antifungals
  • Topical antifungals
  • Topical antifungals
  • Topical antifungals
  • Oral antifungals (> 3-4 nails involved or involvement of lunula)
 
  • Studies
    • potassium hydroxide (KOH) prep with blue fungal stain of scale
      • branching septate hyphae
  • Treatment
    • management approach
      • topical antifungals are often applied without topical steroids
      • if used with steroids, may lead to tinea incognito
        • persistent tinea infection without clinical symptoms due to steroid use
        • may be confused with psoriasis or ezcema
    • oral antifungals
      • griseofulvin
      • itraconazole or fluconazole
      • terbinafine
    • topical antifungals
      • terbinafine cream
      • ketoconazole cream
      • clotrimazole cream
  • Complications
    • bacterial superinfection
Tinea versicolor
  • Introduction
    • organism
      • Malassezia spp. (Pityrosporum spp.)
      • yeast-like fungi
    • pathogenesis
      • the infection can damage melanocytes, resulting in hypopigmentation, hyperpigmentation, and pink patches
    • risk factors
      • summer
      • humid weather
      • sweating
      • using body oils
      • immunosuppression
  • Presentation
    • can be pruritic but not as pruritic as dermatophytic infections
    • macules or plaques with irregular borders and overlying fine scale
      • back, chest, neck, and face are commonly affected
      • often present as areas of hypopigmentation
    • inability to tan these areas
  • Studies
    • KOH prep
      • budding cells with multibranching hyphae
      • “spaghetti and meatballs” appearance
    • Wood lamp
      • affected areas will fluoresce
  • Treatment
    • topical selenium sulfide
    • topical antifungals (first-line)
      • ketoconazole
    • oral antifungals (second-line)
      • itraconazole
      • fluconazole
Sporotrichosis
  • Introduction
    • organism
      • Sporothrix schenckii
      • dimorphic and cigar-shaped budding yeast with branching hyphae and rosettes of conidia
    • demographics
      • children and young adults
    • transmission
      • direct contact
        • break in skin, often with thorns or splinters
        • via animal bites or scratches
    • risk factors
      • close contact with vegetation (gardening)
      • classically via traumatic introduction with a plant’s thorn (i.e., roses)
      • hunting in the wild
      • immunosuppression
  • Presentation
    • pustule, abscess, or ulcer at site of inoculation
    • nodules along draining lymphatics (nodular lymphangitis)
    • can be disseminated to the rest of the body
  • Studies
    • fungal culture in Sabouraud agar
    • periodic acid-Schiff or methenamine silver stain
      • oval or cigar-shapped budding yeast cells
      • septate hyphae with clusters of characteristic conidia formation (“daisy flowers”)
  • Differential diagnosis
    • tularemia
      • similar to sporotrichosis, tularemia may present with an ulcerated lesion
      • unlike sporotrichosis, tularemia may also have a widespread maculopapular rash, painful conjunctivitis, pharyngitis, and gastrointestinal symptoms
  • Treatment
    • itraconazole
      • first-line
    • potassium iodide
      • adjuvant therapy to itraconoazole
    • amphotericin
      • disseminated disease

 

 

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