Superficial Fungal Infections Flashcards
(46 cards)
1
Q
Dermatophyte definition
A
- superficial fungal infection (incapable of penetrating subcutaneous tissue)
- skin, hair, nails
- fungus b/d keratin as nitrogen source
- “tinea”
2
Q
Dermatophyte infection of the:
- body
- groin
- head
- beard
- hand
- feet
- nail
A
- tinea corporis
- tinea cruris
- tinea capitis
- tinea barbae
- tinea manuum
- tinea pedis
- tinea unguium
3
Q
MC genera of dermatophyte
A
trichophyton
4
Q
KOH procedure
A
- clean and moisten skin with alcohol swab
- collect scale with angled #15 blade
- place scale on a slide
- add drop KOH and heat to dissolve keratin
- view
5
Q
What procedure to do next if KOH is negative but still suspect a fungus?
A
fungal culture
- benefits: can find source (ID animal) of infection and select most suitable treatment
6
Q
What are diagnostic features of KOH exam of tinea?
A
“spaghetti and meatballs”
- buds and strands of hyphae
7
Q
Limitations of KOH exam
A
- too small of sample
- sample taken from area without fungus
- previous anti fungal treatment
- it’s hard, relies on trained eye, false negatives are not uncommon
8
Q
Tinea capitis
- definition
- epidemiology
- how is it spread
A
- dermatophytosis of scalp and hair
- MC AA children (children in general)
- spread through direct contact with animals, humans, fomites
9
Q
Tinea capitis
- MC dermatophyte
A
- in US: trichophyton tonsurans
10
Q
Tinea capitis
- clinical presentation
A
- non-inflammatory (black dot, seborrheic)
- inflammatory (kerion)
Or both! - broken hair is prominent feature
- often lymphadenopathy: cervical MC, post auricular, occipital
11
Q
Tinea capitis
- kerion
A
- painful, inflammatory, boggy mass with broken hair follicles
- usually dt untreated tinea
- may discharge pus
- often confused with bacterial infection
- higher risk of scarring than other tinea capitis forms
12
Q
Tinea capitis
- treatment
A
- topical agents ineffective!
- Griseofulvin
- treat until no visual evidence + 2 weeks
- av 6-12 weeks tx
13
Q
Tinea pedis
- define
A
- athletes foot
- MC fungal infection in developed countries
- MC fungus: trichophyton rubrum
- thrives in warm, moist environment
- public showers and gyms common source
14
Q
Tinea pedis
- three clinical patterns
A
- interdigital
- moccasin
- vesiculobullous
15
Q
Tinea pedis
- Interdigital
A
- MC
- scaling and redness between toes
- possible maceration
16
Q
Tinea pedis
- moccasin
A
- aka chronic hyperkeratotic
- sharply marginated scale
- distributed along borders of feet, heels, soles
- often associated with onychomycosis: if find on nail, look at foot and vice versa
17
Q
Tinea pedis
- moccasin type presentation
A
- often “one hand, two feet”
- affected hand: unilateral fine scaling in the crease
- if find any of these sx, check both feet and both hands
18
Q
Tinea pedis
- vesiculobullous
A
- grouped, 2-3 mm vesicles
- often on arch or instep
- itchy or painful
- scale on sole
- delayed hypersensitivity immune repose to a dermatophyte
19
Q
Tinea pedis
- treatment hygiene
A
- dry area after bathing
- change socks and alternate shoes
- wear open shoes
- use OTC anti fungal foot powder
20
Q
Tinea pedis
- topical treatments
A
- imidazoles: clotrimazole or miconazole
- Allylamines: terbinafine, naftifine, butenafine
- Allylamines better sustained cure rate but more $$
21
Q
Tinea pedis
- when to refer
A
- failed response to hygiene, imidazole and allylamine
- large body surface involved
- atypical areas of body involved
22
Q
Tinea corporis
A
- ringworm
- dermatophytosis of the skin, usually the trunk and limbs
- often pruritic
- lesion margin most active, central healing
- take scraping from red scaly margin for KOH
- check bottom of feet for tinea pedis
23
Q
Tinea cruris
A
- variant of tinea corporis
- jock itch
- may lack scale dt scrotal occlusion
- check feet soles for tinea pedis
- similar presentation to corporis but in the groin
24
Q
Tinea corporis treatment
A
- topical antifungals: apply until resolution + 2 weeks (4-6 weeks total)
- imidazoles (clotrimazole and miconazole)
- Allylamines (naftifine, terbinafine, butenafine)
25
Tinea corporis
| - when to initiate oral antifungals
- poor response to topical agents
- animal is suspected source of infection
- large body surface area involved
- use culture to guide therapy
- Terbinafine is drug of choice
26
Tinea Unguium
- aka onychomycosis
- dermatophyte infection of the nail bed
- usually starts with tinea pedis
- responds poorly to topical antifungals
27
Onychomycosis
- MC cause
- presentation
- distal type is distal subungual onychymycosis (DSO)
- thickened nail, sublingual debris, separation of nail plate from nail bed
* * Usually not on all the nails!!
- Trichophyton rubrum
28
Two presentations of onychomycosis
- Superficial white onychomycosis: less common, respond to topical therapy
- Proximal subungual onychomycosis: may herald immunosuppression
29
Important step before treating onychomycosis
- confirmation that it is a fungal infection!
| - may mimic other conditions such as psoriasis
30
How to confirm onychomycosis
- fungal culture (preferred bc can help direct tx options)
- KOH exam of subungual debris
- nail clipping/biopsy submitted for histologic exam
31
First line treatment for onychomycosis
- Terbinafine
- lots of ADR: hepatotoxicity, drug interactions, skin reactions, etc.
- clinical cure only seen 50% of the time
32
When to refer onychomycosis
- negative on multiple cultures and or histology
- pattern of nail dystrophy is not typical for fungal infection, esp if other rashes present
- culture-positive fails compliant first-line therapy
33
Tinea versicolor
- description
- etiology
- NOT a dermatophyte
- colonization of Malassezia, a yeast (normal resident in keratin and hair follicles)
- annual summer occurrence common
34
Tinea versicolor
| - presentation
- well-demarcated
- tan/salmon hypo- or hyper pigmented patches
- MC trunk and arms
- Macules grow, coalesce into asymmetric distribution
- Scale but not always visible until rub with finger or scalpel blade (diagnostic feature is evoked scale)
35
Tinea versicolor
| - presentation in diff colored skin
- untanned caucasian: salmon-colored or brown
- tanned caucasian: pale
- darker skin: hyper or hypo pigmented
36
Microscopy of tinea versicolor
Spaghetti and meatballs :)
37
First line treatment of tinea versicolor
Topical treatment
- Shampoo: selenium sulfide, ketoconazole, zinc pyrithione. Apply, wait 10 minutes, rinse
- Imidazole cream: ketaconazole, clotrimazole.
38
Tinea veriscolor maintenance therapy
- many pts relapse
- If have had more than one previous episode, recommend maintenance therapy
- Topicals 1-2 x week
39
Intertrigo
| - overview
- inflammation of skin folds
- inframammary, gluteal cleft, inguinal crease, folds under pannus
- 10% complicated by Candida yeast colonization
40
Intertrigo
| - classic sx
- burn > itch
- satellite macules, papules, pustules around erythema in teh fold
- KOH exam may reveal pseudohyphae (fungal culture more sensitive than KOH for candida)
41
Intertrigo
| - prevention
- keep intertriginous areas dry, clean, cool
- dry areas after bathing
- weight loss if obese
- wear loose clothing, cotton
42
Intertrigo
| - Treatment
- Imidazoles: miconazole, clotrimazole, econazole
- polyene: nystatin (only for candida)
* * Allylamines (terbinafine and naftifine) are not effective vs. candida yeast
43
Review
| - when to perform KOH prep
- annular skin lesions to rule out a dermatophyte
| - if KOH negative, perform fungal culture
44
Review
| - how long to treat tinea capitis
- beyond clinical clearance
45
Review
| - defining feature of intertrigo
- satellite macules, papules, pustules at perimeter or erythema
46
Review
| - What is tinea versicolor NOT
- TINEA
| - it's malessezia furor yeast
