Eczema Flashcards
Why is eczema an important condition to know about?
- It’s common
- increasing prevalence
- It’s chronic
- It’s costly
What is eczema?
- A common inflammatory skin condition.
- Commonly affects flexural areas.
- Multiple types and a spectrum of severity
What is the epidemiology of eczema?
- Overall prevalence is 4% in Western countries
- Most commonly appears in babies and children (by adult life 60% have cleared)
- Increasing prevelance
What criteria is used to define atopic eczema?
Modified Hanifin and Rajka criteria
What is the definition of atopic eczema?
-An itchy skin condition in the last 12 months
Plus 3 of the following:
- Onset before age 2
- History of flexural involvement
- History of generally dry skin
- History of other atopic disease (Asthma/hayfever)
- History in 1st degree relative if under 4 yrs
What is the triad of atopy?
- Asthma
- Hayfever
- Eczema
What is the pathogenesis behind atopic eczema?
- Genetics
- Epidermal barrier dysfunction
- Environmental factors
What gene plays a key role in atopic eczema?
Filaggrin gene
What atopic family history may there be in atopic eczema?
- Atopic eczema
- Asthma
- Hayfever (allergic rhinitis)
- Food allergy
What is the pathology of atopic eczema?
- Spongiosis (intercellular oedema) within the epidermis.
- Acanthosis (thickening of the epidermis).
- Inflammation - Superficial perivascular lymphohistiocytic infiltrate.
What are the causes of acute flares?
- Viral illness - or period poor health
- Stress
- Environmental triggers (heat, cold, allergens (house dust mite, cat/dog dander))
- Food allergies
What are the clinical features of atopic eczema?
- Itch, redness, scaling, papules, vesicles
- Flexural – however can involve all body sites
- Babies – usually starts on the face
- Chronic changes
What are the chronic changes involved in atopic eczema?
- Lichenification
- Plaques
- Fissuring
What exogenous types of eczema are there?
- Contact dermatitis (allergic/ irritant)
- Lichen simplex
- Photoallergic or photpaggravated eczema
What endogenous types of eczema are there?
- Atopic
- Discoid
- Venous
- Seborrheic dermatitis
- Pompholyx
- Juvenile plantar dermatitis
- Asteatotic
What is allergic contact dermatitis caused by?
- Type 4 Hypersensitivity
- Delayed hypersensitivity – can take 48-72 hrs to develop reaction
Describe the process of a type 4 hypersensitivity reaction.
- Antigen presenting cells take allergen to LN and present to naive T cells
- Clonal expansion of these T cells, (released into blood stream)
- When these T cells next encounter hapten
- Mast cell degranulation, vasodilatation and neutrophils
In irritant contact dermatitis, what can skin be injured by?
Friction
- Micro-trauma
- Cumulative
Environmental factors
- Cold
- Over exposure to water
- Chemicals such as acids, alkalis, detergents and solvents
What occupations are at particular risk of irritant contact dermatitis?
- Hairdressers
- NHS staff
- Cleaners
- Nappy rash
- Medical/nursing students!
Describe how patch testing is carried out.
- Potential allergens applied (no needles involved!)
- Baseline/standard series – applied to all patients
- Applied Monday
- Remove Wednesday
- Re-assess Friday
- Expect most allergens at 96 hour (Friday reading)
Describe the features of seborrheic dermatitis in infants.
- Distinctive pattern
- Predilection for scalp, proximal flexures.
- <6months age usually.
- Often clears within weeks of treatment
What is another name for seborrheic eczema?
Chronic dermatitis
Describe the presentation of seborrheic eczema in adults.
- Malassezia yeast increased in the scaly epidermis of dandruff and seborrehoic dermatitis.
- Red, sharply marginated lesions covered with greasy looking scales.
- Distinctive distribution – areas rich in supply of sebaceous glands (scalp, face, upper trunk).
What can be a precursor for seborrheic eczema?
Dandruff. May gradually progress through redness, irritation and increased scaling
