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
What mutation that affects skin barrier function is associated with atopic dermatitis/ eczema
mutations in fillagrin gene that result in severe/early onset disease (ichthyosis vulgaris)
What is the relevance of the defective skin barrier in eczema
The defective skin barrier allows access/sensitisation to allergen and promotes colonisation by microorganisms
What happens to the dermatitis in atopic dermatitis
- The normal dermis has a small amount of lymphocytes and other immune cells but in skin with eczema there is a vast infiltrate visible
- TH2 cells, DC, macrophages and mast cells are involved (probably attracted to lesions by stressed keratinocytes)
What happens to keratinocytes in eczema
Keratinocytes in the epidermis start detaching from one another, becoming rounder and the intercellular spaces widening between them
What causes the histological spongiotic change in eczema
- If the eczema has come on acutely, this separation may be so severe that vesicles form
- Under the microscope, this makes the epidermis look like a sponge, hence ‘spongiotic’ change
How does eczema change with age
Childhood predominance: symptoms tend to become less severe with age
What areas are commonly affected in eczema of infants vs teens
Infants - face is common site
Older kids/adults - flexor distribution (antecubital fossa and posterior knee)
Atopic dermatitis/ eczema clinical features
- The skin is itchy, erythematous, and oozing
- May be vesicles, which may have crusted over (infections)
- Eventually, the skin becomes dry and flaky
- Repeated scratching causes lichenification (thick, leathery skin, also called lichen simplex et chronicus)
Eczema can present differently in different skin colours. What is a common presentation in black people
Nodular Pruigo (well define itchy, lichenified nodules)
Secondary infection can occur in patients with atopic dermatitis/ eczema. What would indicate this? name 2 examples
- Crusting => Staph aureus
- Monomorphic punched-out lesions => Herpes simplex virus (eczema herpeticum)
What is eczema herpeticum
Herpes simplex virus infection in patients with eczema, presenting as monomorphic punched-out lesions
Atopic dermatitis/ eczema diagnosis
Clinical diagnosis, diagnostic criteria…
Itching plus 3 or more of:
- Visible of flexural rash (cheeks/extensor surfaces in infants)
- History of flexural rash (cheeks/extensor surfaces in infants)
- Personal history of atopy (or first degree relative if <4 years)
- Generally dry skin
- Onset before age 2
Atopic dermatitis/ eczema conservative management
Break the itch-scratch cycle!
- Avoid allergens & triggers e.g. soap substitutes
- Keep the area cool & dry
- Sedating antihistamine can reduce itching and aid sleep
- Liberal emollients should be applied frequently
- Psychological support may be needed
Mild atopic dermatitis/ eczema topical management
Mild Topical steroid
Moderate atopic dermatitis/ eczema topical management
- Moderate topical steroid e.g. betamethasone valerate 0.025% or clobetasone butyrate 0.05%
- If face affected start with mild steroid in that area
Severe atopic dermatitis/ eczema topical management
- Potent topical steroid e.g. betamethasone valerate 0.1% on inflamed areas
- For more sensitive areas moderate potency e.g. betamethasone valerate 0.025% or clobetasone butyrate 0.05% max 5 days use
- Consider occlusive dressings
Last line/ secondary care atopic dermatitis/ eczema management
- Phototherapy UVB - mainly
- Systemic immunosuppression
- Biological agents (for atopic - target IL-4/IL-13)
What is discoid eczema
- Eczema occuring in circular or oval patches (well-defined)
- Patients are often atopic
- Very often infected
What are the two different causes of photo-induced/ sensitive eczema
- Reaction to UV light (Well defined edge e.g. cut-off collar)
- Patients often atopic
- Can also occur secondary to photosensitising drugs
What is lichen simplex dermatitis
Caused by chronic itching & is characterised by well demarcated, erythematous patches, and plaques of thickened leathery skin
What causes stasis (varicose) dermatitis
- This is eczema associated with chronic venous insufficiency (venous hypertension), usually affecting the gaiter area
- Increased hydrostatic pressure of the blood results in extravasion of RBCs
what clinical features would you expect in stasis dermatitis
Associated skin change include venous ulcers, lipodermatosclerosis, and hemasiderosis
Stasis dermatitis management
Compression stockings
What is dyshidriotic eczema (pompholyx eczema)
- Occurs when there is a very sudden acute flare up of eczema and the spongiotic vesicles join together
- Dermatological emergency and may complicate atopic eczema
Dyshidriotic eczema (pompholyx eczema) presentation
- There will be widespread redness (90%)
- Tiny blisters develop in hands (classically sides of fingers) and feet
- Intensely itchy
Seborrheic eczema clinical features
- The skin is flakey with a fine scale, oily, and erythematous
- There is usually minimal pain or stinging or itch
- The scale may coalesce into thicker plaques
- It tends to affect the face (especially hairline, nasolabial fold, and brow area) in adults
What is dandruff
Dandruff is the common term used to describe a mild, non-inflamed form of seborrheic dermatitis
What is cradle cap
Infantile seborrheic dermatitis
How does cradle cap appear
diffuse, yellow, greasy scale, coalescing into plaques on the scalp/groin/armpit
Cradle cap treatment
- Emollients (such as olive oil) loosen the scales, which can then be brushed off
- Antifungal shampoos may be used if the issue persists
- Tends to resolve with age
