Flashcards in Dermatology Deck (89)
What is atopic dermatitis?
Inflammatory skin condition characterised by dry pruritic skin which a chronic relapsing course
What is the aetiology of atopic dermatitis?
- Multifactorial aetiology, combination of genetic susceptibility and environmental factors contributing to disease development
- Defects in skin's barrier function and immune dysregulation following allergen exposure are thought to be key components in the development of this disease
What is the epidemiology of atopic dermatitis?
- Usually presents in childhood
- Remission is notes by 15 years of age mostly but relapse may occur later
What are the presenting symptoms of atopic dermatitis?
- Presence of risk factors: under 5yrs, FHx, allergic rhinitis, asthma, antihelminth tx in utero
- Xerosis (dry skin)
- Sites of skin involvement: Infants- cheeks, forehead, scalp. Children: flexures esp. wrist, ankle
What are the signs of atopic dermatitis on examination?
- Keratosis pilaris
What are the investigations for atopic dermatitis?
Clinical diagnosis: features of dermatitis
- Allergy testing
- IgE levels: elevated
- Skin biopsy
What is basal cell carcinoma?
Commonest form of skin malignancy, also known as 'rodent ulcer'
What is the aetiology of basal cell carcinoma?
- Prolonged sun exposure or UV radiation
- Associated with abnormalities of the patches/hedgehog intracellular signalling cascade, as seen in Gorlin's syndrome (naevoid basal cell carcinoma syndrome).
- Other risk factors include photosensitising pinch, tar and arseninc
What is the epidemiology of basal cell carcinoma?
- Common in those with far skin and areas of high sunlight exposure
- Common in elderly, rare before age of 40
- Lifetime risk in Caucasians is 1:3
What are the presenting symptoms of basal cell carcinoma?
A chronic slowly progressive skin lesion usually on the face but also on the scalp, ears or trunk
What are the signs of basal cell carcinoma on examination?
- Nodulo-ulcerative (most common): Small glistening translucent skin over a coloured papule that slowly enlarges (early) or a central ulcer ('rodent ulcer') with raised pearly edges. Fine telangiectatic vessels often run over the tumour surface. Cystic change may be seen in larger more protuberant lesions.
- Morphoeic: Expanding, yellow/white waxy plaque with an ill-defined edge (more aggressive)
- Superficial: Most often on trunk, multiple pink/brown scaly plaques with a fine 'whipchord' edge expanding slowly; can grow to more than 10cm in diameter
- Pigmented: Specks of brown or black pigment may be present in any type of basal cell carcinoma
What are the investigations for basal cell carcinoma?
Biopsy is rarely necessary (Dx is based mainly on clinical suspicion)
What is contact dermatitis?
An allergic or irritant skin reactions caused by an external agent
What is the aetiology of contact dermatitis?
The top 5 allergens found to cause contact dermatitis in children were nickel sulfate, ammonium persulfate, gold sodium thiosulfate, thimerosal, and toluene-2,5-diamine
What is the epidemiology of contact dermatitis?
- Rare in first few months of life, but prevalence increases with age
- Gender differences may be attributed to social and environmental factors; females are more likely to have nickel sensitivity because of increased wearing of jewellery, and males are more likely to have chromate sensitivity from occupational exposure.
What are the presenting symptoms of contact dermatitis?
- Risk factors: occupation with frequent exposure to water of caustic material, atopic dermatitis
- Previous similar episodes
- Acute onset
- Affecting hands and face
- Affecting sun-exposed skin
- Sparing of non-exposed areas of skin
What are the signs of contact dermatitis on examination?
- Vesicles and bullae
- Lichenoid lesions
- Corrosion or ulceration
What are the investigations for contact dermatitis?
- Patch testing: positive result show inflammation graded on a 1+ to 3+ scale within 2-7 days of application
- Repeated open application test pr provocative use test: Inflammation or dermatitis at application site
What is eczema?
A pruritic papulovesicular skin reaction to endogenous or exogenous agents
What is the aetiology of Eczema?
Numerous varieties caused by a diversity of triggers
- Exogenous: Irritant, contact, phototoxic
- Endogenous: Atopic, seborrhoeic, pompholyx, varicose, lichen simplez
- Irritant: Prolonged skin contact with a cell-damaging irritant
- Contact: Type IV delayed hypersensitivity to allergen
- Seborrhoeic: Pityrosporum yeast
- Varicose: Increased venous pressure in lower limbs
What is the epidemiology of eczema?
- Prevalence: 4%
- Atopic: Onset is commonly in first year of life
What are the presenting symptoms of eczema?
- Itching (can be severe)
- Heat, tenderness, redness weeping, crusting
- Enquire into occupational exposures or irritants used at home (e.g. bleach)
- Enquire into family/personal history of atopy (e.g. asthma, hay fever, rhinitis)
What are the signs of acute eczema on examination?
- Poorly demarcated erythematous oedematous dry scaling patches
- Papules, vesicles with exudation and crusting, excoriation marks
What are the signs of chronic eczema on examination?
- Thickened epidemis
- Skin lichenification
- Changes in pigmentation
What are the signs of different types of eczema on examination?
- Contact & irritant: Eczema reaction occurs where irritant/allergent comes into contact with skin
- Atopic: Particularly affects face and flexures
- Seborrhoeic: Yellow greasy scales on erythematous plaques, particular in the nasolabial folds, eyebrows, scalp and presternal area
- Pompholyx: Acute and often recurrent vesicobullous eruption on palms and soles
- Varicose: Eczema of lower legs, associated with marked varicose veins
- Nummular: Coin shaped on legs and trunk
- Asteototic: Dry, 'crazy' pairing' pattern
What are the investigations for contact eczema?
Skin patch testing: Disc containing postulated allergen in diluted and applied to back for 48h
- Positive if allergen induces a red raised lesion
What are the investigations for atopic eczema?
Swab for infected lesions (bacteria, fungi, viruses)
What is erythema multiforme?
An acute hypersensitivity reaction of the skin and mucous membranes
- Stevens-Johnson syndrome is a severe form with bullous lesions and necrotic ulcers
What is the aetiology of erythema multiforme?
- Drugs: Sulfonamides, penicillin, phenytoin, barbiturates
- Infection: Viral (HSV, EBV, coxsackie, adenovirus, ORF), Bacterial (M. pneumoniae, Chlamydiae), Fungal (Histoplasmosis)
- Inflammatory: Rheumatoid arthritis, SLE, sarcoidosis, UC, systemic vasculitis
- Malignancy: Lymphomas, leukaemia, myeloma