Superficial Mycoses Flashcards
Superficial fungal infections are defined by their…
…anatomic location, not their etiology.
Dermatophytoses (tinea syndromes)
• Three etiologic genera
- Epidermophyton
- Microsporum
- Trichophyton
- All anamorphic ascomycetes with septate hyphae, containing macro and microconidia
• Cause infection of the keratinized tissues
- hair, skin, nails
• Transmission occurs from direct contact with infected keratinized tissue onto breaks in the skin
- person-to-person (anthropophilic), fomites, soil (geophillic), animals (zoophilic)
Pathogenesis of dermatophytosis
- Organisms require keratin for growth
- They colonize the cornified epithelium of the skin but are unable to penetrate deeper
- They do not involve the mucosa
- They spread outward as nutrients are consumed, forming a ring of inflammation
Tinea capitis
• Occurs principally in children
- ages 3-7 years
- transmission through sharing combs, brushes, headgear
- Most cases due to Trichophyton tonsurans
- Infection begins with invasion of stratum corneum of the scalp, then invades the hair follicles
- Three patterns of infection
- Ectothrix
- fungal spores form a sheath around the hair shaft
- hair shafts weaken and break, cause alopecia
- Endothrix
• fungal spores invade the hair shaft
- Favus
• hyphae within the shaft without spores
Clinical presentation of tinea capitis
Issues with tinea capitis
- Because of invasion of hair shafts, systemic antifungal therapy is required
- Sterilization of fomites (hair brushes, combs) is recommended
- Occipital and cervical lymphadenopathy is frequently present
- Rare in adults
Tinea barbae
• Occurs in the bearded area of men
- Barber’s itch, ringworm of the beard
- Earlier, common and due to contaminated barbershop razors
- Now, rare and mostly due to zoonotic dermatophytes, T. verrucosum or T. mentagrophytes
- Inflammatory patches with pustules a common presentation
- Tinea faciei
- Tinea of the face in non-bearded individuals
Tinea corporus
- Most common in children & young adults
- Present world-wide
- more common is warm, humid areas
- Most cases due to Trichophyton rubrum
- Infection of the trunk and limbs (excluding hands and feet)
- Usual presentation is scaly non-inflammatory plaques (“ringworm”)
Tinea cruris
• Dermatophytosis of the inguinal region
- “Jock itch”
- The scrotum & penis in men are not involved
- but may spread to the perineum & gluteal folds
- Common in warm, humid climates & in crowded conditions
- More common in men
- Most cases due to T. rubrum
- Pruritis may be severe
Tinea pedis
• Most common dermatophytosis
- Athlete’s foot, ringworm of the feet
- More common in males, & with increasing age
- Most cases due to T. rubrum and T. mentagrophytes
- Epidermophyton floccosum causes some cases
•Three clinical patterns
- moccasin
- interdigital
- inflammatory
Clinical presentation of tinea pedis
Tinea manuum
• Similar to the “moccasin” presentation of tinea pedis but involving the hands
- scaling, erythematous
- less common than foot involvement
• Often evident on feet but frequently involves only one hand
- “one hand two feet” syndrome
Tinea unguium
- Dermatophyte infection of the nails
- “Onychomycosis”
- broader term that encompasses all fungal nail infections
• Prevalence 3-13%
- increases with age
- toenails are most commonly affected
- most of these are due to dermatophytes
- Characterized by accumulation of debri beneath the nail and an opaque, chalky or yellow nail
- begins with distal and lateral infection, spreading proximally
Malassezia spp
• Lipophilic dimorphic fungi that are part of the normal skin flora
- basidiomyces, generally in yeast form
- requires fat to grow
• Pityriasis (tinea) versicolor
- patchy hypo
- & hyperpigmented macules on the trunk
- “spaghetti & meatballs” appearance
- may fluoresce orange-yellow under Wood’s lamp
- Seborrheic dermatitis, dandruff, folliculitis
- Topical selenium sulfide helpful
- Topical or systemic antifungals useful
Diagnosis of superficial fungal infection
- Wood’s lamp
- KOH preparations
- Culture
Biopsy
Wood’s lamp
- Shining an ultraviolet (UV) lamp onto the lesion
- Most dermatophytes seen in the U.S. do not fluoresce
- Useful for
- distinguishing erythrasma (due to Corynebacterium minutissimum)
- fluoresces coral red
- dermatophyte infections do not
- cases of tinea capitis due to Microsporum spp fluoresce bright green
- pityriasis versicolor (M. furfur) demonstrates a pale yellow-green fluorescence in ⅓ of cases
Potassium hydroxide (KOH) preparations
• Allows visualization of hyphae in lesion
- septate
- branching
• Procedure
- Scrape keratinized tissue from border of lesion or obtain involved hair or subungual debris
- Transfer to glass slide
- Add 10% or 20% KOH, place coverslip
- Warm slide for several minutes to dissolve keratin
- Examine under medium power (400x)
Culture
- Time-consuming and expensive
- Useful if diagnosis is in doubt
- Procedure
- obtain sample as for KOH
- send for fungal culture (Sabouraud’s dextrose agar)
- usually takes 14 - 21 days
- specific diagnosis based on culture & microscopic morphology
• particularly of the asexual macro and microconidia
Topical treatment for tinea infections
Systemic therapy for tinea infections
Therapy for onychomycosis
Oropharyngeal candidiasis
• Risks
- HIV-1 infection
- Systemic antibiotics
- Corticosteroids
• Presents in 3 stages
- angular cheilitis
- erythematous candidiasis
- pseudomembranous candidiasis (thrush)
Esophageal candidiasis
• Occurs in highly immunosuppressed patients
- HIV-1 infection
- CD4 cell count <100/µl
- Dysphagia, odynophagia, retrosternal pain
- Diagnosis requires esophageal visualization
- culture
- biopsy
Vulvovaginal candidiasis
• May occur in immunologically normal women
- pregnancy, oral contraceptives
• Risk factors for severe disease similar to those for oropharyngeal candidiasis
- often a presentation for women with HIV-1 infection
• Diagnosis
- Examination
• vaginal mucosal erythema with adherent white discharge
- Microscopic
- 10% KOH preparation demonstrates yeast in 50-70%
- culture non-specific
Cutaneous candidiasis
• Candida paronychia
- occurs after prolonged exposure of the hands to moisture
- redness and purulence along lateral nail fold
• Candida intertrigo
- occurs in those with diabetes, prolonged antibiotics, obesity
- axillae, groin, skin under pannus
- scrotum involved
- satellite lesions common
