Cutaneous and Subcutaneous Mycoses

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

Tinea (Dermatophytes)

Tinea (Dermatophytes)
	Tinea capitis	Tinea corporis (“ringworm”)	Tinea cruris (“jock itch”)	Tinea pedis (“athlete’s foot”)	Tinea unguium (onychomycosis)
Location	HeadScalp	Torso	Inguinal	Feet	Nails
Clinical characteristics	LymphadenopathyItchy 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 thickeningNail discolorationNo pain or itching
Risk factors	African American or Carribbean descent	Contact with infected pet	Adolescent and adult malesPhysical activities that cause sweating	Occlusive footwearWarm and moist environment	Occlusive footwearWarm and moist environmentImmunosuppressionCommunal bathing
Treatment	Oral antifungals (topicals will not penetrate hair follicles)	Topical antifungals	Topical antifungals	Topical antifungals	Topical antifungalsOral 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

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