Fungi and infestations Flashcards
What are the 3 categories of fungal infections?
Superficial - epidermis
Deeper infections - dermis + subcutaneous tissue
Systemic infections
What are the most common causative fungi seen in dermatology?
Dermatophytes
What are the three genera of dermatophytes?
microsporum
trichophyton (most common)
epidermophyton
Through what do dermatophytes invade and live in?
Keratinised stratified squamous epithelium
What are potential reservoirs of dermatophytes?
humans
animals
soil
What are the lay and medical terms for dermatophyte infection?
Lay - ringworm
Medical - tinea
What types of tinea infection are there?
tinea corporis (tinea of the hairless skin)
tinea cruris (groin)
tinea manuum (hand)
tinea pedis (foot)
onychomycosis (tinea of the nails, a.k.a. tinea unguium)
tinea capitis (head)
What is the most common type of tinea infection?
tinea pedis
Which demographic is tinea capitis most common in?
Afro-Caribbeans due to increased genetic risk
List diseases than can be confused with tinea?
Psoriasis
Nummular dermatitis
Erythrasma
Candidiasis
How can psoriasis be differentiated from tinea?
In tinea there will NOT be nail pitting.
although onycholysis can occur in both
Which areas are at risk of candida infection?
Mouth
Genitals
Around nails
Which groups are particularly at risk of candida infection?
Young / Old
Immunosuppressed
Diabetics
On antibiotics / steroids
What is the Ix of choice for suspected fungal skin infections?
Skin scraping (essentially any infested part of skin which can the be MC+S)
What are the indications for systemic anti-fungals?
If nail,
scalp or
hair are infected
if a widespread skin infection
if immunocompromised
What is the most effective agent for tinea (dermatophyte infection)?
Terbinafine
Through what route are azoles metabolised?
Via the liver
In which patients must you be careful prescribing systemic azoles to?
Those with poor liver function as the azole will thus be metabolised slower
Which azole can be used as a shampoo?
Fluconazole
Why is ketoconazole generally not used systemically?
As it inhibits androgen synthesis leading to gynaecomastia
Why is griseofulvin rarely used anymore?
As it is more fungistatic than cidal
For what is griseofulvin licensed for?
Orally treat Tinea
What are the two adverse affects of griseofulvin?
Can induce a photosensative rash
Can cause drug interactions as is metabolised by the liver
Is griseofulvin oral or topical?
Oral. It is ineffective topically
What are the treatments for candidiasis?
Systemic –> Polyenes: Nystatin or Amphotericin B
Topical –> Azoles: Clotrimazole or fluconazole
What are malassezia furfur?
Commensal fungi (yeasts)
What are the two cutaneous manifestations of malassezia furfur?
pityriasis vesicolor
seborrhoeic dermatitis
Who is pityriasis vesicolor commonly seen in the UK?
People coming home from holiday
How common is relapse in pityriasis vesicolor?
Common to relapse
How is Pityriasis vesicolor treated?
Topical antifungals
Selenium shampoo
Intraconzole
How common is Seborrhoeic dermatitis?
Fairly common
What is the typical distribution of seborrhoeic dermatitis?
Symmetrical on the face
Scalp - cradle cap (in young children), dandruff (adults)
Flexures
What is the treatment for seborrhoeic dermatitis?
Topical azoles
Low potency topical corticosteroids
How does scabies spread?
Human to human contact
not via clothing or dirty toilet seats
What is the severe form of scabies known as? (who is it seen in)
crusted scabies
(seen in immuno-compromised or elderly patients)
has a high mite load
What are the signs of scabies infection?
Itchy papules (often excoriated)
Burrows
What is the inflammation in scabies caused by?
Mite faeces
What is a unique physical sign of scabies in children? (and what causes it)
blistering of the palms and soles
due to stong host response to the infestation
What is the treatment for scabies?
Permethrin for 12hrs
or
Malathion for 12hrs
wash clothes and linen
treat all contacts simultaneously (including health care workers)
What is an adverse outcome post-scabies treatment? (how is it treated?
post-scabies eczema
this is treated as per normal eczema
What causes head lice?
pediculosis capitis
What do pediculosis capitis feed on?
Feed on blood in the scalp
What can pediculosis capitis transmit?
Transmit staph aureus &
strep pyogenes
How is pediculosis capitis transmited?
Human to human contact
What are the signs of head lice?
pruritis
eggs (nits) or live lice seen on hair
erythema
papules
excoriations
What is the treatment for pediculosis capitis?
Removal (hair conditioner, fine comb)
Pediculicides (malathion) - this is not that effective
How is tinea investigated?
Skin scraping
Nail clippings/subungul debrisd
Hair pluckings
Wood’s light (emits UV-A)
What are the systemic antifungals?
Terbinafine
Azoles (Itraconazole)
Griseofulvin
What are the topical antifungals?
Terbinafine
Azoles (Ketoconazole)
Polyenes (Nystatin)
What are the sigde effects of terbinafine?
There arn’t any common ones
What are the signs of pityriasis vesicolor?
Hypo- or hyper-pigmented patches
Mild scaling
Mostly on the trunk
