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Dermatology > Fungal Skin Infections > Flashcards

Fungal Skin Infections Flashcards

1
Q

What is candida?

A

Candida = group of yeasts (fungus) that commonly infect the skin.
=> ‘candida’ = white colour of culture
=> most common = candida albicans

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2
Q

Who is at risk of candida?

A

Candida depends on a living host for survival.

Candida part of normal flora of the gut
=> But if the host’s defences are lowered, candida causes infection of the mucosa (lining of the mouth, anus and genitals) and skin.

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3
Q

What are the types of candida rash?

A

=> Oral candidiasis (oral thrush)

=> Angular cheilitis

=> Vulvovaginal candidiasis (genital infection in women)

=> Balanitis (penile infection)

=> Intertrigo (skin fold infections)

=> Napkin dermatitis (nappy or diaper rash)

=> Chronic paronychia (nail fold infection)

=> Onychomycosis (nail plate infection)

=> Chronic mucocutaneous candidiasis

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4
Q

What are the predisposing factors for candida infection?

A

=> Infancy or old age

=> Warm climate

=> Occlusion eg, plastic pants (babies), nylon pantyhose (women), dental plates

=> Broad-spectrum antibiotic treatment

=> High-oestrogen contraceptive pill or pregnancy

=> Diabetes mellitus

=> Cushing syndrome

=> Iron deficiency

=> General debility e.g. from cancer or malnutrition

=> Underlying skin disease eg, psoriasis, lichen planus

=> Immunodeficiency e.g. HIV, steroids, chemo

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5
Q

What is invasive candidiasis?

A

Spread of candida through the bloodstream (candidaemia) and infection of heart, brain, eyes, bones, and other tissues.

=> usually in immunocompromised

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6
Q

How is candida diagnosed?

A

Microscopy and culture of skin swabs and scrapings aids diagnosis.

=> Results of laboratory tests must be correlated with the clinical presentation

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7
Q

How is candida managed?

A

Pre-disposing factors must be treated.

For uncomplicated candidiasis:

=> Topical therapy i.e.
topical Azoles (clotrimazole, econazole, miconazole, or ketoconazole)

OR

=> Nystatin (oral candidiasis)

For severe candidiasis:
=> oral fluconazole (150mg x 2 doses)

For recurrent candidiasis:
=> Induction course of oral fluconazole (150mg x 3 doses)
=> After treatment as required

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8
Q

What is pityriasis versicolor?

A

Pityriasis versicolor = common yeast infection of the skin presenting with flaky discoloured patches on the chest and back

The term pityriasis describes skin conditions in which the scale appears similar to bran.

There are multiple colours of pityriasis versicolor hence ‘versicolor’

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9
Q

Who is at risk of pityriasis versicolor?

A

Affects young adults

Men > women

Can also affect children, adolescents, and older adults.

More common in hot, humid climates

Affects people that perspire heavily.

May clear in winter and recur each summer.

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10
Q

What are the clinical features of pityriasis versicolor?

A

=> Affects trunk, neck, and/or arms

=> Coppery brown, paler than surrounding skin, or pink patches

=> Pale patches may be more common in darker skin - known as pityriasis versicolor alba.

=> Usually asymptomatic but in some people = mildly itchy

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11
Q

What is the cause of pityriasis versicolor?

A

Malassezia (found on normal skin flora).

Usually malassezia grow sparsely in the seborrhoeic areas (scalp, face and chest) without causing a rash.
=> unknown why they grow more actively on the skin surface of patients prone to pityriasis versicolor

  1. Brown-type pityriasis versicolor => Malassezia induce enlarged melanosomes (pigment granules) within basal melanocytes
  2. The white or hypopigmented type of pityriasis versicolor => due to a chemical produced by malassezia that diffuses into the epidermis and impairs the function of the melanocytes.
  3. The pink type of pityriasis versicolor => mildly inflamed due to dermatiits induced by malassezia or its metabolites. *Pink pityriasis versicolor and seborrhoeic dermatitis may co-exist, as both are associated with malassezia.
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12
Q

How is pityriasis versicolor diagnosed?

A

Clinical diagnosis

Can be confirmed via microscopy of skin scrapings showing spherical yeast and short pseudohypae (meatballs & spaghetti)

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13
Q

How is pityriasis versicolor treated?

A

Mild pityriasis versicolor is treated with topical antifungal agents

=> Topical azole cream/shampoo (econazole, ketoconazole)

=> Anti-dandruff shampoos containing selenium sulfide may be used as body wash

=> Terbinafine gel

=> Ciclopirox cream/solution

=> Propylene glycol solution

=> Sodium thiosulphate solution

^ Medicines should be applied to all the affected areas before bedtime for as long as directed (usually between 3 days and about two weeks, depending on extent of the rash)

Oral itraconazole for resistent / extensive cases

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14
Q

What are dermatophytes?

A

Dermatophytes (tinea) fungi invade and grow in dead keratin.

They form an expanding annular lesion due to lateral growth (hence the name ‘ringworm’)

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15
Q

What are the 3 main types of dermatophytes?

A
  1. Trichophyton
  2. Microsporum
  3. Epidermophyton
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16
Q

How is dermatophytes / tinea transmitted?

A

Transmitted to humans via:

=> other people (anthropophillic)

=> animals (zoophilic)

=> soil (geopphilic)

*therefore clinical appearance depends on infecting organism, site affected and host reaction

17
Q

Tinea infection classified according to site:

  1. Tinea coporis = body
  2. Tinea facei = face
  3. Tinea barbae = beard
  4. Tinea cruris = groin
A
  1. Tinea manuum = hand
  2. Tinea pedis = foot
  3. Tinea capitis = scalp
  4. Tinea unguium = nails
    * multiple sites can be affected at once so skin, hair and nails should be examined
18
Q

How does tinea coporis present?

A

Asymmetrical, scaly inflamed patches with clearer centre

Scaly raised border

Sometimes vesciles / pustules

19
Q

Why should you not give steroids in a tinea infection?

A

Topical steroids reduce inflammation and mask clinical signs => allowing the infection to spread = tinea incognito

Stopping steroids = flare of infection

20
Q

How does tinea cruris present?

A

Intensely itchy rash in the groin with a scaly border

May extend to the thighs

Men > Women

21
Q

What is tinea pedis colloquially known as?

How does it present?

A

Tinea pedis aka athlete’s foot
=> very common in adults

Presents with:

=> white, macerated and fissured skin

=> confined to two webs

=> can extend to the soles & side of feet causing dryness, scaling and erythema

=> toenails often affected

=> flares in hot weather causing pustules and blisters

22
Q

Which group is tinea capitis most common in?

How does it spread?

A

Most common dermatophyte infection in young children esp. black African origin

Spread via close contact i.e. in schools or sharing brushes/clippers

i. Fungus confined to hair shaft = endothrix
ii. Fungus spread our over the hair surface = ectothrix

23
Q

What is the clinical presentation of tinea capitis (scalp ringworm)?

A

Presentation varies from:

i. Mild diffuse scaling with no hair loss (similar to dandruff)
ii. More typical bald, scaly patches with broken hairs

Increased host response causes pustules and an inflammatory exudate

24
Q

What is the difference between tinea unguium and onychomycosis?

A

Onychomycosis = broad term for fungal nail infection

Tinea unguium = dermatophyte infection of the finer or toe nail

25
Q

What is the most common organism causing tinea unguium?

A

Trichophyton rubrum

26
Q

How does tinea unguium present?

Who does it affect?

A

Usually aymptomatic

Tinea unguium presents with:

=> Dystrophic, thick (subungual hyperkeratosis) changes in affected nail

=> Discolouration (white / yellow / beige)

=> Infection starts on lateral or distal edges then progresses proximally

=> Nail plate may be destroyed in advanced disease

27
Q

What are the differentials for tinea unguium?

A

Nail psoriasis

Traumatic nail dystrophy (may co-exist with fungal infection)

28
Q

How do you manage dermatophyte infection?

A
  1. Localised tinea coporis:

=> antifungal cream i.e. clotrimazole, miconazole or terfinafine for 1-2 weeks

=> Nystatin is ineffective

  1. Widespread infection, tinea pedis, tinea manuum, tinea capitis:

=> oral antifungal i.e. itraconazole or terbinifine for 1-2 months

  1. Toenail tinea infections:

=> prolonged oral antifungal therapy i.e. terfinafine for 3-6 months

*clears up 80% of infection but may relapse

29
Q

How is a diagnosis of dermatophyte confirmed?

A

Skin scrapings taken from active margin or across the affected area

Clippings from proximal crumbly white area of affected nails

Plucked hairs or scrapings for diagnosis of scalp tinea

Specimens transported in folded paper to keep dry & prevent bacterial contamination

=> Microscopy & mycological culture confirm the diagnosis + identify the organism

Dermatology (18 decks)

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