Dermatology Flashcards
Define basal cell carcinoma
Commonest form of skin malignancy, also known as rodent ulcer
Explain the aetiology/risk factors of basal cell carcinoma
- MAIN RISK FACTOR: prolonged sun exposure or UV radiation
- Seen in Gorlin’s syndrome
- Other risk factors:
o Photosensitising pitch
o Tar
o Arsenic
Summarise the epidemiology of basal cell carcinoma
- COMMON in those with FAIR SKIN
- Common in areas of high sunlight exposure
- Common in the elderly
- Rare before the age of 40 yrs
- Lifetime risk in Caucasians = 1 in 3
Recognise the presenting symptoms of basal cell carcinoma
- A chronic slowly progressive skin lesion
- Usually found on the:
o FACE
o Scalp
o Ears
o Trunk
Recognise the signs of basal cell carcinoma on physical examination
- Nodulo-ulcerative (MOST COMMON)
o Small glistening translucent skin over a coloured papule
o Slowly enlarges
o Central ulcer with raised pearly edges
o Fine telangiectasia over the tumour surface
o Cystic change in larger lesions
- Morphoeic
o Expanding
o Yellow/white waxy plaque with an ill-defined edge
o More aggressive than nodulo-ulcerative
- Superficial
o Most often on trunk
o Multiple pink/brown scaly plaques with a fine edge expanding slowly
- Pigmented
o Specks of brown or black pigment may be present in any BCC
Identify appropriate investigations for basal cell carcinoma
- Biopsy is RARELY necessary
* Diagnosis is mainly on clinical suspicion
Define contact dermatitis
An inflammatory skin reaction in response to an external stimulus, acting either as an allergen or an irritant.
Explain the aetiology/risk factors of contact dermatitis
- There are TWO main types of contact dermatitis that may co-exist:
o ALLERGIC - a delayed type IV hypersensitivity reaction, which occurs after sensitisation and subsequent re-exposure to the allergen
o IRRITANT - an inflammatory response that occurs after damage to the skin, usually by chemicals
- Common ALLERGENS
o Cosmetics (e.g. fragrances)
o Metals
o Topical medications
o Textiles
- Common IRRITANTS
o Detergents and soaps
o Solvents
Summarise the epidemiology of contact dermatitis
- 4-7% of all dermatology consultations
* Hands are most commonly affected
Recognise the presenting symptoms and signs of contact dermatitis
- HANDS are the most frequently affected
- Contact dermatitis from clothing can occur in the axillae, groins and feet
- Redness of skin
- Vesicles and papules in the affected area
- Crusting and scaling of skin
- Itching of an affected area
- Fissures
- Hyperpigmentation
- Pain or burning sensation
- Make sure you do a thorough OCCUPATIONAL HISTORY
Identify appropriate investigations for contact dermatitis
- NO investigations necessary most of the time
* Some may need patch testing
Define eczema
A pruritic papulovesicular skin reaction to endogenous and exogenous agents
Explain the aetiology/risk factors of eczema
- There are lots of types because there are many different triggers
- Exogenous
o Irritants (e.g. nappy rash)
o Contact (delayed type 4 hypersensitivity reaction to an allergen)
o Atopic
- Endogenous
o Atopic
o Seborrhoeic
o Pompholyx (a type of eczema that affects the hands and feet)
o Varicose
o Lichen simplex
- Varicose - due to increased venous pressure in lower limbs
Summarise the epidemiology of eczema
- Contact - prevalence: 4%
* Atopic - onset in first year of life, childhood incidence: 10-20%
Recognise the presenting symptoms of eczema
- Itching
- Heat
- Tenderness
- Redness
- Weeping
- Crusting
- Ask about occupational exposure to irritants 9eg.. Bleach)
- Ask about personal/family history of atopy (e.g. asthma, hay fever)
Recognise the signs of eczema on physical examination
- Acute
o Poorly demarcated erythematous oedematous dry scaling patches
o Papules
o Vesicles with exudation and crusting
o Excoriation marks
- Chronic
o Thickened epidermis
o Skin lichenification
o Fissures
o Change in pigmentation
- Based on type of eczema
o Atopic - mainly affects face and flexures
o Seborrhoeic - yellow greasy scales on erythematous plaques. Commonly found on eyebrows, scalp, presternal area
o Pompholyx - vesiculobullous eruption on palms and soles
o Varicose - associated with marked varicose veins
o Nummular - coin shaped, on legs and trunk
o Asteatotic - dry, crazy paring pattern
Identify appropriate investigations for eczema
- Contact Eczema
o Skin patch testing - a disc containing allergens is diluted and applied on the skin for 48 hrs. It is positive if it causes a red raised lesion
- Atopic Eczema
o Lab testing e.g. IgE levels
Define 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
Explain the aetiology/risk factors of erythema multiforme
- Degeneration of basal epidermal cells
- Development of vesicles between cells in the basement membrane
- Lymphocytic infiltrate around the blood vessels and at the dermo-epidermal junction
- A precipitating factor is only identified 50% of the time
- Precipitating Factors:
o Drugs - e.g. sulphonamides, penicillin, phenytoin
o Infection - e.g. HSV, EBV, adenovirus, chlamydia, histoplasmosis
o Inflammatory - e.g. rheumatoid arthritis, SLE, sarcoidosis, ulcerative colitis
o Malignancy - e.g. lymphomas, leukaemia, myeloma
o Radiotherapy
Summarise the epidemiology of erythema multiforme
- Any age group
- Mainly in CHILDREN and YOUNG ADULTS
- TWICE as common in MALES
Recognise the presenting symptoms of erythema multiforme
- Non-specific prodromal symptoms of upper respiratory tract infection
- Sudden appearance of itching/burning/painful skin lesions
- Skin lesions may fade leaving pigmentation
Recognise the signs of erythema multiforme on physical examination
- Classic target (bull’s eye) lesions with a rim of erythema surrounding a paler area
- Vesicles/bullae
- Urticarial plaques
- Lesions are often symmetrical and distributed over the arms and legs including the palms, soles
and extensor surfaces
- Stevens-Johnson syndrome is characterised by:
o Affecting > 2 mucous membranes (e.g. conjunctiva, cornea, lips, mouth, genitalia)
o Systemic symptoms (e.g. sore throat, cough, fever, headache, myalgia, arthralgia, diarrhoea/vomiting)
o Shock (hypotension and tachycardia)
Identify appropriate investigations for erythema multiforme
- Usually unnecessary - erythema multiforme is very much a clinical diagnosis
- Bloods
o High WC, eosinophils, ESR/CRP
- Imaging - exclude sarcoidosis and atypical pneumonia
- Skin biopsy - histology and direct immunofluorescence if in doubt about diagnosis
Define erythema nodosum
Panniculitis (inflammation of subcutaneous fat tissue) presenting as red or violet subcutaneous nodules
