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Dermatology 1 > Superficial Fungal Infections > Flashcards

Superficial Fungal Infections Flashcards

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1
Q

Dermatophyte definition

A
  • superficial fungal infection (incapable of penetrating subcutaneous tissue)
  • skin, hair, nails
  • fungus b/d keratin as nitrogen source
  • “tinea”
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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
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3
Q

MC genera of dermatophyte

A

trichophyton

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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
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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

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6
Q

What are diagnostic features of KOH exam of tinea?

A

“spaghetti and meatballs”

- buds and strands of hyphae

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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
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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
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9
Q

Tinea capitis

- MC dermatophyte

A
  • in US: trichophyton tonsurans
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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
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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
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12
Q

Tinea capitis

- treatment

A
  • topical agents ineffective!
  • Griseofulvin
  • treat until no visual evidence + 2 weeks
  • av 6-12 weeks tx
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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
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14
Q

Tinea pedis

- three clinical patterns

A
  • interdigital
  • moccasin
  • vesiculobullous
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15
Q

Tinea pedis

- Interdigital

A
  • MC
  • scaling and redness between toes
  • possible maceration
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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
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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
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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
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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
Q

Tinea corporis

- when to initiate oral antifungals

A
  • 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
Q

Tinea Unguium

A
  • aka onychomycosis
  • dermatophyte infection of the nail bed
  • usually starts with tinea pedis
  • responds poorly to topical antifungals
27
Q

Onychomycosis

  • MC cause
  • presentation
A
  • 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
Q

Two presentations of onychomycosis

A
  • Superficial white onychomycosis: less common, respond to topical therapy
  • Proximal subungual onychomycosis: may herald immunosuppression
29
Q

Important step before treating onychomycosis

A
  • confirmation that it is a fungal infection!

- may mimic other conditions such as psoriasis

30
Q

How to confirm onychomycosis

A
  • fungal culture (preferred bc can help direct tx options)
  • KOH exam of subungual debris
  • nail clipping/biopsy submitted for histologic exam
31
Q

First line treatment for onychomycosis

A
  • Terbinafine
  • lots of ADR: hepatotoxicity, drug interactions, skin reactions, etc.
  • clinical cure only seen 50% of the time
32
Q

When to refer onychomycosis

A
  • 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
Q

Tinea versicolor

  • description
  • etiology
A
  • NOT a dermatophyte
  • colonization of Malassezia, a yeast (normal resident in keratin and hair follicles)
  • annual summer occurrence common
34
Q

Tinea versicolor

- presentation

A
  • 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
Q

Tinea versicolor

- presentation in diff colored skin

A
  • untanned caucasian: salmon-colored or brown
  • tanned caucasian: pale
  • darker skin: hyper or hypo pigmented
36
Q

Microscopy of tinea versicolor

A

Spaghetti and meatballs :)

37
Q

First line treatment of tinea versicolor

A

Topical treatment

  • Shampoo: selenium sulfide, ketoconazole, zinc pyrithione. Apply, wait 10 minutes, rinse
  • Imidazole cream: ketaconazole, clotrimazole.
38
Q

Tinea veriscolor maintenance therapy

A
  • many pts relapse
  • If have had more than one previous episode, recommend maintenance therapy
  • Topicals 1-2 x week
39
Q

Intertrigo

- overview

A
  • inflammation of skin folds
  • inframammary, gluteal cleft, inguinal crease, folds under pannus
  • 10% complicated by Candida yeast colonization
40
Q

Intertrigo

- classic sx

A
  • 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
Q

Intertrigo

- prevention

A
  • keep intertriginous areas dry, clean, cool
  • dry areas after bathing
  • weight loss if obese
  • wear loose clothing, cotton
42
Q

Intertrigo

- Treatment

A
  • Imidazoles: miconazole, clotrimazole, econazole
  • polyene: nystatin (only for candida)
    • Allylamines (terbinafine and naftifine) are not effective vs. candida yeast
43
Q

Review

- when to perform KOH prep

A
  • annular skin lesions to rule out a dermatophyte

- if KOH negative, perform fungal culture

44
Q

Review

- how long to treat tinea capitis

A
  • beyond clinical clearance
45
Q

Review

- defining feature of intertrigo

A
  • satellite macules, papules, pustules at perimeter or erythema
46
Q

Review

- What is tinea versicolor NOT

A
  • TINEA

- it’s malessezia furor yeast

Dermatology 1 (19 decks)

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