12 - Dermatology 1: Skin infections Flashcards
What are the layers of the skin?
- epidermis
- dermis
- hypodermis (SC fat)
What is the function of the skin?
- provide anatomical barrier
- main method of heat regulation
- sensory input
- storage for lipids and water
- drug absorption
- waste excretion
What are commensal flora?
- normal colonisation that prevent pathogens in healthy hosts
- mainly bacteria and fungi on skin (staphylococci and candida)
What is oily skin?
- increased secretion form sebaceous glands
- more bacterial colonisation
- skin becomes heavier and thicker
- more risk of pore blockage = more spots
- less likely to wrinkle and age
What is a comedone?
- blackhead
- build up of keratin and sebum
- blocked pores oxidise which gives black appearance
- is a feature of acne vulgaris
What are examples of bacterial infections of the skin?
- furuncles
- carbuncles
- acne
- erysipelas
- impetigo
What are furuncles?
- infection of skin that presents with pockets filled with pus
- caused by s aureus
- red, painful and swollen
- should be drained, do not require antibiotics
What are carbuncles?
Furuncles that are grouped together
What is folliculitis?
Furuncle in a hair follicle
What is acne?
Lesions arising from
- comedones
- papules
- pustules
- nodules
- inflammatory cysts
Who is most affected by acne?
Teenagers aged 13-18 (80% experience)
What are the causes of acne?
- follicular sensitivity to testosterone (increases during puberty)
- propionibacterium acnes overgrows and leads to infection
- scars can form if cysts rupture
What makes acne worse?
- contraceptive pills (containing progesterone)
- greasy skin cleansers
- systemic steroids
- anticonvulsant drugs
- squeezing spots
What is used as local management of acne?
- reduce excess skin oil (gentle soap cleansers)
- antibacterial agents (benzoyl peroxide, retinoids, antibiotic lotions)
What is sued as systemic management of acne?
- antibiotics (tetracycline based)
- retinoids (isotretinion)
- hormone manipulation (anti-androgens)
What is erysipelas?
- presents with defined raised order, may blister and peel
- systemic symptoms include fever and shivering
- caused by streptococcus pyogenes
- can progress to necrotising fasciitis or septic shock
How do you manage erysipelas?
Systemic antibiotics (oral or IV)
What is impetigo?
- highly infectious skin disease caused by staphylococcal or streptococcal bacteria
- presents with crusty red blister appearance
- associated with eczema
How do you manage impetigo?
- topical antibiotics (sometimes systemic)
- antibiotic choice is based on culture
What are examples of viral skin infections?
- HSV
- shingles
- molluscum contagiosum
- warts
- measles
- rubella
- fifth disease
- roseola
- hand, foot and mouth
- HIV
- kaposi’s sarcoma
What are the different types of herpes virus infections?
- HSV (perioral or genital)
- shingles (herpes zoster)
- roseola (HHV6)
- kaposi’s sarcoma (HHV8)
What is a HSV infection?
- affects single dermatome
- activated by trauma (physical, chemical, light, being run down)
- perioral or genital
- present as blister
How do you treat HSV infection?
Acyclovir
What is shingles?
- caused by herpes zoster virus (can be recurrent)
- affects single dermatome
- causes significant pain (neural inflammation)
- pain can persist after rash is gone (post herpetic neuralgia)
How do you treat shingles?
High does acyclovir
What is mollucsum contagiosum?
- caused by a pox virus (MCV)
- presents with clusters of small papules in warm, moist areas, 1-6mm in size
- resolve spontaneously in 1-2 years
- usually found in children and infants or adults with HIV
What are warts?
- usually caused by HPV types 1-3
- spread by contact
- if immunocompetent then most resolve spontaneously
How do you treat warts?
- excision
- cryosurgery
- keratolysis
What are examples of fungal skin infections?
- athlete’s foot
- nail infections
- ringworn
- intertrigo
- pityriasis versicolor
What is athlete’s foot?
- mix of fungal and bacterial infection
- common between toes or in groin
- present with scaling and sogginess of skin
- can be prevented by keeping skin dry, clean and damage free
How do you treat athlete’s foot?
Antifungal or antibacterial cream (eg miconazole)
What is onycholysis?
- nail bed fungal infection
- commonly caused by tinea unguium
- presents with nail bed becoming malformed, thick and crumbly
- can be seen with athlete’s foot
How do you treat onycholysis?
- excise damaged nail
- systemic antifungals
What is ringworm?
- if found on the groin caused by tinea cruris (spread from foot)
- if found on the body caused by tinea corporis (caught from infected animals)
- if found on scalp caused by tinea capitis (leads to hair loss, mainly young children)
How do you treat ringworm?
Antifungal cream or shampoo (if scalp affected)
What is intertrigo?
- fungal infection due to chafing in moist body folds (under breasts, armpits, inner thighs)
- presents with redness of skin
How do you treat intertrigo?
Topical antifungal cream (clotrimzole or miconazole)
What is pityriasis versicolor?
- caused by pityrosporum orbiculare (usually harmless commensal, involved in cradle cap)
- presents with patchy skin pigmentation (pale red or brown)
How do you treat pityriasis versicolor?
- topical antifungal (ketoconazole as wash or shampoo)
- systemic antifungal (itraconazole)
What are examples of skin infestations?
- scabies
- lice
What are scabies?
- infection by the scabies mite
- contracted by skin-to-skin contact
- mites borrow into skin between fingers and on wrists
- presents with red “burrows” on skin, itch and rash that can appear on trunk and legs
- can develop into secondary impetigo
How do you treat scabies?
- topical chemical insecticides (eg benzyl benzoate, permethrin)
- applied to whole body below chin
- all close contacts should be treated even if asymptomatic
What are lice?
- 3 types (head, pubic, body)
- transmitted by close contact or shared items
What is the treatment for head lice?
- most commonly affect children and spread to rest of family
- hair should be combed with fine toothed comb
What is the treatment for body lice?
- personal and clothing hygiene (hot water washing and drying)
- topical chemical insecticides (permethrin)
