Ezcema Flashcards
Eczema vs dermatitis
Skin lesions with similar clinical & pathological features
but different pathogenetic mechanisms (ie different causes)
Describe the acute phase of eczema
papulovesicular
erthematous (red) lesions
oedema (spongiosis)
ooze or scaling & crusting
Describe the chronic phase of eczema
thickening (lichenification)
elevated plaques
Increased scaling
Contact allergic dermatitis pathogenesis & histology
Pathogenesis - Delayed type (type 4) h/s reaction
Histology Spongiotic dermatitis
Contact irritant dermatitis pathogenesis & histology
Pathogenesis - Trauma eg soap, water
Histology - spongiotic dermatitis
Atopic dermatitis (eczema) pathogenesis & histology
Pathogenesis - Genetic & environmental factors resulting in inflammation
Histology - spongiotic dermatitis
Drug related dermatitis pathogenesis & histology
Pathogenesis - Type 1 or 4 h/s reaction
Histology - spongiotic dermatitis & eosinophils
Photo-induced dermatitis pathogenesis & histology
Lichen simplex dermatitis pathogenesis & histology
Stasis dermatitis pathogenesis & histology
Contact allergic dermatitis pathophysiology
- Langerhans cells in the epidermis are exposed to an allergy on the skin & express the antigen on their MHC II molecules
- They then present the antigen to Th cells in the dermis
- The sensitised Th cells migrate into lymphatics and then to regional nodes where antigen presentation is amplified
- When exposed to the allergen again, they migrate & infiltrate the dermis & cause inflammatory cytokine release & cell mediated cytotoxicity
Contact allergic dermatitis clinical features
Itchy, eczematous rash (vesicles, fissures, erythema), typically 24-48 hours after exposure that may extend beyond the boundaries of the immediate contact
Contact allergic dermatitis diagnosis
Patch testing - allergens prepared onto Finn chambers which are applied on the back and removed after 48 hours, readings at 48 and 96 hours
How is the clinical presentation of allergic vs irritant contact dermatitis different
- In allergic, the rash may extend beyond the boundaries of immediate contact…
- In allergic, there is a sensitisation phase & so they may have never had the problem in the past…
- In allergic, there is a specific allergen…
This is not the case in irritant contact dermatitis
What is irritant contact dermatitis
Non specific physical irritation causing eczema/dermatitis
What occupations are commonly associated with irritant contact dermatitis
hairdressers, health care staff, builders and cleaners
Irritant contact dermatitis clinical features
- Eczematous rash localised to the direct area of contact
- There may be burning, pain, and stinging
- May have coexisting allergic contact/ atopic dermatitis
A nappy rash is an example of irritant contact dermatitis. What are of the skin would be spared
Flexure will be spared (due to urine)
Irritant contact dermatitis investigations
- Clinical diagnosis, attempt to identify triggers from history
- If trigger can’t be identified, patch testing may be required
What would cause irritant contact dermatitis around the lips
Lip lick chelitis
What is the main feature of atopic eczema
Pruritus
What other conditions are associated with atopic dermatitis/ eczema
other atopic diseases e.g. asthma, allergic rhinitis, food allergy
Describe atopic dermatitis/ eczema
- Chronic inflammatory disorder of the skin
- Characterised by dermal inflammation (dermatitis) with resultant spongiotic change in the epidermis histologically
- Chronic features including epidermal acanthosis, hyperkeratosis, and parakeratosis
What three factors occur in combination with atopic dermatitis/ eczema
Eczema is a combination of decreased skin barrier function, environmental factors and immunology