Superficial Fungal Infections Flashcards
Dermatophyte definition
- superficial fungal infection (incapable of penetrating subcutaneous tissue)
- skin, hair, nails
- fungus b/d keratin as nitrogen source
- “tinea”
Dermatophyte infection of the:
- body
- groin
- head
- beard
- hand
- feet
- nail
- tinea corporis
- tinea cruris
- tinea capitis
- tinea barbae
- tinea manuum
- tinea pedis
- tinea unguium
MC genera of dermatophyte
trichophyton
KOH procedure
- 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
What procedure to do next if KOH is negative but still suspect a fungus?
fungal culture
- benefits: can find source (ID animal) of infection and select most suitable treatment
What are diagnostic features of KOH exam of tinea?
“spaghetti and meatballs”
- buds and strands of hyphae
Limitations of KOH exam
- 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
Tinea capitis
- definition
- epidemiology
- how is it spread
- dermatophytosis of scalp and hair
- MC AA children (children in general)
- spread through direct contact with animals, humans, fomites
Tinea capitis
- MC dermatophyte
- in US: trichophyton tonsurans
Tinea capitis
- clinical presentation
- non-inflammatory (black dot, seborrheic)
- inflammatory (kerion)
Or both! - broken hair is prominent feature
- often lymphadenopathy: cervical MC, post auricular, occipital
Tinea capitis
- kerion
- 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
Tinea capitis
- treatment
- topical agents ineffective!
- Griseofulvin
- treat until no visual evidence + 2 weeks
- av 6-12 weeks tx
Tinea pedis
- define
- athletes foot
- MC fungal infection in developed countries
- MC fungus: trichophyton rubrum
- thrives in warm, moist environment
- public showers and gyms common source
Tinea pedis
- three clinical patterns
- interdigital
- moccasin
- vesiculobullous
Tinea pedis
- Interdigital
- MC
- scaling and redness between toes
- possible maceration
Tinea pedis
- moccasin
- 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
Tinea pedis
- moccasin type presentation
- 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
Tinea pedis
- vesiculobullous
- grouped, 2-3 mm vesicles
- often on arch or instep
- itchy or painful
- scale on sole
- delayed hypersensitivity immune repose to a dermatophyte
Tinea pedis
- treatment hygiene
- dry area after bathing
- change socks and alternate shoes
- wear open shoes
- use OTC anti fungal foot powder
Tinea pedis
- topical treatments
- imidazoles: clotrimazole or miconazole
- Allylamines: terbinafine, naftifine, butenafine
- Allylamines better sustained cure rate but more $$
Tinea pedis
- when to refer
- failed response to hygiene, imidazole and allylamine
- large body surface involved
- atypical areas of body involved
Tinea corporis
- 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
Tinea cruris
- 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
Tinea corporis treatment
- topical antifungals: apply until resolution + 2 weeks (4-6 weeks total)
- imidazoles (clotrimazole and miconazole)
- Allylamines (naftifine, terbinafine, butenafine)
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
Tinea Unguium
- aka onychomycosis
- dermatophyte infection of the nail bed
- usually starts with tinea pedis
- responds poorly to topical antifungals
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
Two presentations of onychomycosis
- Superficial white onychomycosis: less common, respond to topical therapy
- Proximal subungual onychomycosis: may herald immunosuppression
Important step before treating onychomycosis
- confirmation that it is a fungal infection!
- may mimic other conditions such as psoriasis
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
First line treatment for onychomycosis
- Terbinafine
- lots of ADR: hepatotoxicity, drug interactions, skin reactions, etc.
- clinical cure only seen 50% of the time
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
Tinea versicolor
- description
- etiology
- NOT a dermatophyte
- colonization of Malassezia, a yeast (normal resident in keratin and hair follicles)
- annual summer occurrence common
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)
Tinea versicolor
- presentation in diff colored skin
- untanned caucasian: salmon-colored or brown
- tanned caucasian: pale
- darker skin: hyper or hypo pigmented
Microscopy of tinea versicolor
Spaghetti and meatballs :)
First line treatment of tinea versicolor
Topical treatment
- Shampoo: selenium sulfide, ketoconazole, zinc pyrithione. Apply, wait 10 minutes, rinse
- Imidazole cream: ketaconazole, clotrimazole.
Tinea veriscolor maintenance therapy
- many pts relapse
- If have had more than one previous episode, recommend maintenance therapy
- Topicals 1-2 x week
Intertrigo
- overview
- inflammation of skin folds
- inframammary, gluteal cleft, inguinal crease, folds under pannus
- 10% complicated by Candida yeast colonization
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)
Intertrigo
- prevention
- keep intertriginous areas dry, clean, cool
- dry areas after bathing
- weight loss if obese
- wear loose clothing, cotton
Intertrigo
- Treatment
- Imidazoles: miconazole, clotrimazole, econazole
- polyene: nystatin (only for candida)
- Allylamines (terbinafine and naftifine) are not effective vs. candida yeast
Review
- when to perform KOH prep
- annular skin lesions to rule out a dermatophyte
- if KOH negative, perform fungal culture
Review
- how long to treat tinea capitis
- beyond clinical clearance
Review
- defining feature of intertrigo
- satellite macules, papules, pustules at perimeter or erythema
Review
- What is tinea versicolor NOT
- TINEA
- it’s malessezia furor yeast
