Superficial Mycoses Flashcards
(33 cards)
1
Q
Superficial fungal infections are defined by their…
A
…anatomic location, not their etiology.
2
Q
Dermatophytoses (tinea syndromes)
A
• 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)
3
Q
Pathogenesis of dermatophytosis
A
- 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
4
Q
Tinea capitis
A
• 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
5
Q
Clinical presentation of tinea capitis
A
6
Q
Issues with tinea capitis
A
- 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
7
Q
Tinea barbae
A
• 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
8
Q
Tinea corporus
A
- 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”)
9
Q
Tinea cruris
A
• 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
10
Q
Tinea pedis
A
• 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
11
Q
Clinical presentation of tinea pedis
A
12
Q
Tinea manuum
A
• 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
13
Q
Tinea unguium
A
- 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
14
Q
Malassezia spp
A
• 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
15
Q
Diagnosis of superficial fungal infection
A
- Wood’s lamp
- KOH preparations
- Culture
Biopsy
16
Q
Wood’s lamp
A
- 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
17
Q
Potassium hydroxide (KOH) preparations
A
• 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)
18
Q
Culture
A
- 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
19
Q
Biopsy
A
- Rarely done
- May be useful
- Intertrigo: Intertrigo is a fancy name for a rash that shows up between the folds of skin.
• may be erythrasma, psoriasis or due to Candida or dermatophytes
- If diagnosis is in doubt or previous therapy has failed
20
Q
Treatment
A
• Superficial fungal infections may be treated
- Topically
Systemically
21
Q
Topical treatment for tinea infections
A
22
Q
Systemic therapy for tinea infections
A
23
Q
Therapy for onychomycosis
A
24
Q
Superficial candidiasis
A
- Candida is part of the normal flora of the gastrointestinal tract and female genital tracts
- Superficial candidiasis occurs
- at extremes of age
- in those with diabetes
- in those with T-cell deficiencies
- under certain environmental conditions
• antibiotic use
25
Oropharyngeal candidiasis
• Risks
- HIV-1 infection
- Systemic antibiotics
- Corticosteroids
• Presents in 3 stages
- angular cheilitis
- erythematous candidiasis
- pseudomembranous candidiasis (thrush)
26
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
27
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
28
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
29
Candida funguria
• Major risk factors
- indwelling urinary catheter
- antibiotic therapy
- (diabetes)
• Treatment
- remove or control risks
- azoles or topical or systemic amphotericin B if symptomatic
• echinocandins do not to reach high levels in urine
30
Treatment of superficial candidiasis
• Remove risk factors
- stop antibiotics
- remove foreign bodies
- treat HIV-1
Topical therapy
- clotrimazole
- nystatin
• Systemic therapy
- oral triazole antifungals
- prolonged use has resulted in development of resistance
31
Topical therapy for mucosal candidiasis
• Oropharyngeal
- Clotrimazole troche 5x/d for 7-14 d
- Nystatin 200,000 units 5x/d for 7-14 d
• Angular cheilitis
- Nystatin/triamcinolone ointment BID
- Clotrimazole/beclamethasone ointment BID
• Vaginal
- Miconazole, clotrimazole cream or suppositories
- Nystatin 100,000 pastilles
- daily for 3-7 days
32
Treatment of cutaneous candidiasis
• Paronychia
- Drainage
- Clotrimazole cream BID x 7 d
- Fluconazole 100 mg daily x 3 d
• Intertrigo
- Clotrimazole cream BID x 7 d
33
Systemic therapy for mucosal candidiasis
• Oropharyngeal
- Fluconazole 100 - 200 mg daily for 7- 10 d
• Vaginal
- Fluconazole 150 mg daily x 3 d
