Flashcards in Eczema Deck (40)
Describe the epidemiology of eczema
• 24% children
• 4% in western countries
• 60% cleared by adulthood
What is eczema?
• A common inflammatory skin condition.
• Commonly affects flexural areas.
• Multiple types and a spectrum of severity
Wide range of external (exogenous) or internal (endogenous) factors can induce the condition
What is another name for eczema?
How is the prevalence of eczema changing?
Increased prevalence of atopic eczema
What is the clinical definition of atopic eczema?
An itchy skin condition in the last 12 months
Plus 3 of:
• Onset before 2yrs
• History of flexural involvement
• H. of generally dry skin
• H. of other atopic disease
What is the pathogenesis of eczema?
• Atopic FH: atopic eczema, asthma, hay fever (allergic rhinitis), food allergy
• Filaggrin gene
• Epidermal barrier dysfunction
• Environmental factors
• Immune system dysregulation - TH2 overactive causing inflammation and leukocyte increase
What are three pathologies on the skin?
• Spongiosis (intercellular oedema) within the epidermis
• Acanthosis (thickening of the epidermis)
• Inflammation - superficial perivascular lymphohistiocytic infiltrate
Describe normal structure of skin layers
• Epidermis - outermost layer of skin
• Dermis - contains blood vessels, lymph vessels, hair follicles and sweat glands
Describe the histology of acute dermatitis
• Intercellular oedema within the epidermis
• Accumulation of intra-epidermal vesicles
• Infiltration of the epidermis with lymphocytes
• Dermal changes include varying degrees of oedema and a superficial perivascular infiltrate with lymphocytes, histiocytes and occasional neutrophils and eosinophils.
Describe the histology of chronic spongiotic dermatitis
• Spongiosis is mild
• Epidermal acanthosis (thickening of epidermis) - psoriasis pattern with hyperkeratosis and hypergranulosis
• Fibrosis of papillary dermis
What is spongiotic dermatitis?
Dermatitis that involves fluid buildup in your skin
Spongiosis is mainly intercellular oedema in the epidermis
What are the clinical features of eczema?
• Pruititus, erythema, scale, papules, vesicles
• Exudate, crusting, excoriation
• Lichenification (thickened skin), plaques, fissuring (split or crack)
Describe the distribution of eczema
• Flexure, neck, eyelids, face, hands and feet
• Tends to spare nappy area
What is excoriation?
Obsessive-compulsive disorder. It is characterised by repeated picking at one's own skin which results in skin lesions.
Name other types of exogenous eczema
• Contact dermatitis (irritant and allergic)
• Lichen simplex
• Photoallergic or photoaggravated
Name other types of endogenous eczema
What is the pathogenesis of allergic contact dermatitis?
1. Antigen presenting cells take hapten/allergen to LN and present to naive T cells
2. Clonal expansion of these T cells, released into blood stream
3. When these T cells next encounter hapten -> mast cell degranulation, vasodilatation and neutrophils
What kind of reaction causes allergic contact dermatitis?
• Type 4 hypersensitivity
• Delayed hypersensitivity (48-72hrs)
What are the two ways the skin is injured by in Irritant Contact Dermatitis?
1. Friction – micro-trauma, cumulative
2. Environmental factors
What are the environmental factors which can cause irritant contact dermatitis?
• Over-exposed to water
• Chemicals; acids, alkalis, detergents and solvents
What test can be used for allergic contact dermatitis?
What are the principles of patch testing?
• Potential allergens applied
• Baseline/standard series – applied to all patients
• Applied Monday, remove Wednesday and re-assess Friday as you're looking for a delayed hypersensitivity reaction
What are the clinical features of seborrhoeic dermatitis (infants)?
• Distinctive pattern
• Scalp, proximal flexures
• < 6months age
• Often clears within weeks of treatment
What are the clinical features of seborrhoeic eczema (adults)?
• Chronic dermatitis.
• Malassezia yeast increased in the scaly epidermis of dandruff
• Red, sharply marginated lesions covered with greasy looking scales.
• Distinctive distribution – areas rich in supply of sebaceous glands (scalp, face, upper trunk)
What do you treat seborrhoeic eczema?
Topical anti-yeast (ketoconazole)
If severe, consider HIV test
What are the clinical features of discoid eczema?
• Circular plaques of eczema.
• Cause often unknown.
• May develop at sites of trauma/irritation.
What are the clinical features of pompholyx/vesiclar eczema?
• Palms and soles
• Intense itch
• < 40yrs
• Sudden onset of crops of vesicles
• Resolution can include desquamation
What are the clinical features of Asteatotic eczema?
• Very dry skin
• Cracked scaly appearance
• Most commonly shins affected
• Climate – heat
• Excessive washing/soaps
What are the clinical features of Venous eczema?
• Stasis eczema or varicose eczema
• Increased venous pressure
• Ankle and lower leg involved
Resolution of oedema can help – compression stockings.